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UPDATED: The errors in Tony Northrups “cheating” accuse video.

 

Well, after watching this we are probably cheated. The guy in this video perhaps misleads people about how mirrorless manufacturers(Sony, Olympus and Panasonic) cheating people in advertising. He stated that Sony, Panasonic and Olympus mislead us with the 135FF equivalent conversion, as well as Fujifilm ISO cheat.

 

 

Tony, the presenter in the video, said these manufacturers should have marked the converted F-number on lenses because of DoF is different while not refering to the lens speed. At the end, he praises the big DSLR brands(Canon & Nikon) as a good honest guy.

His statement seems reasonable. As we know, it is a common sense and important photography principle, aperture controls the light volume through the lens to the sensor, which is what does it work for. However he informed us different terms of them. He thinks aperture is a depth of field(DoF) controller, so that manufactor should have convert the F-number on lens label, such as Panasonic 12-35mm f/2.8 should be labeled 24-70mm f/5.6 due to the MTF has 2x deeper DoF. Seems correct? well, let’s think about when we use M-mode and sunny-16 rule without metering, it would be a problem, because the metering is under 2EV (MTF) or 1EV (APSC).

Do you think Sony, Olympus and Panasonic cheat us?

UPDATE: This is an important update by Ale (Mirrorlessrumors administrator)

There are a couple of logical errors made by Tony Northrup.

First: No one cheats. All company aperture lens info are correct! The Panasonic 12-35mm f/2.8 has a f/2.8 aperture and not a f/5.6 aperture. You don’t have to make the equivalence he says has to be done! Use the Sony A7r and Sony A6000 for the same shot. To get same result the camera automatically sets on both the same ISO and same lens aperture despite the different sensor size. Just to say that the aperture remains CONSTANT and is not relative! There is no equivalence to make on that! 

Please read that article why you cannot apply the aperture equivalence you mention on no other than the “depth of field” and “field of view” only:
http://admiringlight.com/blog/full-frame-equivalence-and-why-it-doesnt-matter/

The focal length and aperture do remain constant!!!!

Second: He says Olympus, Panasonic and Sony do cheat. Nope. All companies use the same kind of measuring aperture for all lens formats (medium format, MFT format, APS-C and so on).

UPDATE of the UPDATE: After re-watching the video I am sure Tony confused “Focal length” with “Field of view” ! It’s the field of view where you can make the equivalence and not the focal length. Tony has been misleaded by the companies because they do that (small) error too. That’s why when he did the math in the video to explain how aperture gets calculated he made the mistake to change the focal length variable. But actually that variable doesn’t change at all! What changes is the “field of view”  which has no influence on aperture. Hope you got the message :)

LIke Admiringlight says:

“I’ve heard many times “Yeah, your 75mm f/1.8 is crap – it’s like a 150mm f/3.6.” No, it’s not, it’s a 75mm lens with an f/1.8 aperture and a field of view that is the same as a 150mm lens on full frame.”

I know Tony had good intentions and I wrote him and hope to will remove the video soon. But please guys, spread the word that what he tells about the equivalence is plain wrong. Don’t worry your f/2.8 MFT or APS-C lens is really a f/2.8 lens!

  • Keiki

    OMG!! This guyyy!! do you live in mars or somthing??
    Get a life dude!!

    • Simen1

      If you want to be taken seriously, try to be serious and factual. Do your math, do your practical comparisons.

    • thedreamcast

      This guy…what? sorry I don’t know him. Is he so famous? huh, I think he now is really famous. :)

  • Hubertus Bigend

    No way I’m going to waste the complete half hour the video takes to explain to me things I know since I bought a Four Thirds DSLR (I’m still using one, by the way, eventually to be replaced by a Micro Four Thirds camera) some two years after Olympus introduced the Four Thirds system.

    Too bad, but only for themselves, that people still don’t get it even if they watched it. It’s impossible that someone who knows that to compare by equivalence you have to

    – multiply focal length by crop factor
    – multiply aperture by crop factor
    – multiply ISO by (crop factor)²

    would earnestly suggest to print those multiplied values onto lenses. But IF manufacturers talk about EQUIVALENT figures, it indeed is and always was cheating to only multiply focal length. Technically interested people who want to really know what’s going on and don’t want to cheat themselves knew that all along, though.

    Oh, and from that, and from other videos I’ve seen from him I know that he would never cite depth of field as the only reason that a multiplied equivalent aperture has to be used to compare equivalent things. It’s light gathering capability as well. F-Stops give you relative apertures, but for depth of field and light gathering capability it’s the light-sensitive area combined with the relative aperture that counts.

    • Simen1

      Its a nice, very straight forward educational video. Nothing new to me either, but due to general confusion around this, many people should see it.

  • hexx

    Yeah and how should they label medium format lenses then? Or sell them with replaceable stickers based on what film or sensor size you use? Utter nonsense – 14mm lens is 14mm lens. F/2.8 aperture is F/2.8 aperture. This is the same guy who also has ‘preview’ of Pentax 645Z on YouTube, yet he has not handled one and that video is also full of similar nonsense.

    • Hubertus Bigend

      You don’t get it, either. All lenses should be labeled for what they are, with their physical focal length and their physical aperture. But IF a manufacturer puts the EQUIVALENT focal length on it, in order to not cheat customers they’d have to put the equivalent aperture alongside it as well.

      • hexx

        Nope, I get it. But aperture information on the lens, is indication of light gathering capacity. DoF is indicated by distance and DoF scale on the lens or on LCD/EVF. People like to confuse these two.

        • Hubertus Bigend

          No, they don’t. But they notoriously get accused of it by people who don’t want to accept reality. And reality is that light gathering ability of a lens is determined by real focal length and real aperture, and that multiplying focal length but not multiplying aperture makes a wrong statement about light-gathering capability, too, not just DoF. What I’ve seen from the video does explain it correctly and thoroughly, you might want to watch it again. To multiply focal length but not aperture breaks physics and maths, it’s as simple as that.

          • hexx

            50mm lens on medium format, 135 format whatever format cameraat ISO 100 and 1/125 shutter speed and f/16 aperture will result in the same exposure on all formats.

          • Hubertus Bigend

            Yes, but the same exposure with the same aperture and the same shutter speed on different formats produces different results. The same exposure with equivalent apertures and equivalent ISOs, though, produces the most similar and comparable results across formats. So that’s how a hypothetical equivalent lens must be defined: with a multiplied focal length and a multiplied aperture. If it isn’t, that hypothetical lens is NOT equivalent.

          • hexx

            You are confusing DoF with aperture. Video states that lenses advertised for smaller formats should have aperture value adjusted to smaller format – that’s what i’m saying is WRONG. Aperture of a lens is the SAME regardless of sensor size it has nothing to do with the sensor/capturing device and is property of lens.

          • Hubertus Bigend

            No, I’m not, and no, the video doesn’t. Watch it again. Video only states IF the manufacturer boasts an EQUIVALENT focal length of his lens, THEN he should add what the equivalent aperture of his hypothetical equivalent lens really would be. Which is, for example, f/11 at 600mm for a Four Thirds 300mm f/5.6 lens. Otherwise, nowhere does the video say the lens should be marked with anything other than 300mm and f/5.6.

          • hexx

            you are still not getting it – there is no such a think as equivalent aperture – aperture does not change. what you are trying to say is what aperture you would need to use to achieve similar/same DoF – two completely different things

          • Hubertus Bigend

            No, it’s still you who doesn’t get it. No one ever claimed aperture would “change”. Remind yourself that focal length doesn’t “change”, either. Those facts notwithstanding, manufacturers boast equivalent focal lengths for their lenses. Meaning: our 300mm lens is like a hypothetical 600mm lens on a full-frame body. But they fail to add that their hypothetical 600mm lens would have to be a f/11 lens, not a f/5.6 lens. A 300mm f/5.6 lens on a Four Thirds sensor DOES IN NO WAY behave like a 600mm f/5.6 lens on a FF body, it behaves IN EVERY RESPECT like a 600mm f/11 lens on a FF body. Do watch the video, it explains the maths and the physics which indeed do not leave any other option.

          • hexx

            i’m giving up :) it’s really pointless (just a suggestion, slap that 300mm lens on your FF body and check if for the same exposure you have to set f/11 aperture – once enlightened we can talk again)

          • Hubertus Bigend

            Sorry, but, again, your “suggestion” is completely beside the point.

            The point is to determine the parameters which define a FF lens which produces the same images and which offers the same options as the MFT lens, because that’s what a manufacturer directly or indirectly claims when boasting an “equivalent” focal length.

            FT: 300mm, f/5.6, ISO 200, 1/500s
            FF: 600mm, f/11, ISO 800, 1/500s

            These parameters, as a rule, are the ones that produce as similar images as they can get out of the two formats.

            So they are the only parameters which can rightfully claim to be equivalent, and more than that, they constitute equivalence only if they come together for focal length, aperture and ISO.

          • madmax

            I think you are a bit confused about the concept of aperture of a lens.
            The maximum theoretical aperture of a lens is the result of dividing two numbers: focal lenght and diameter of the lens. Period. Light gathering capability of a lens is only a function of lens area that depends only on aperture and focal lenght. Nothing to do with you are saying, as “real aperture” is a concept that has to do with lens glass properties (differences between f and T numbers).

          • Hubertus Bigend

            What I called the real aperture is the absolute aperture. The F-Stop aperture is the relative aperture. We don’t need that concept, though. The light gathering capability depends on the relative aperture of a lens (which determines light intensity, the number of photons per square micron, not the total amount of light, i.e. total number of photons) and the light-sensitive area.

      • bousozoku

        135 Format is not the end-all-be-all of formats, though.

        They would spend years trying to figure out the base for equivalency.

        • Hubertus Bigend

          Of course there is no such thing as a “base for equivalency”. Equivalency is a simple relation of physical quantities which is valid between all different sensor sizes. It’s the manufacturers who insist on stating “equivalent” focal-length figures while implicitly meaning “equivalent to full-frame”.

    • Simen1

      The photo communities are too deep in love with focal length, f-numbers and ISO to describe various properties. They really should have changed to field of view in degrees h/v, light gathering area in mm² and grainity in dB but I really don’t see that coming. Its too geeky knowledge for the megapixel buying generation.

      • Hubertus Bigend

        Nice try, but how could a lens be described by field of view if it can and should be used on cameras with different sensor sizes? Do you really think a 50mm f/2 for Four Thirds should be described and labelled differently than a 50mm f/2 for Full Frame?

        I’m all for adding a figure for the image circle a lens is able to illuminate, but I cannot really see a sensible alternative for specifying the lens characteristics which are determined by aperture and focal length.

  • Dummy00001

    They need to put it into a paper book format. Simply add word “holy” before – and the church of equivalency got itself a scripture!

    Seriously though, it’s such a waste of time. None of it is useful. None of it would help people become better photogs.

    • Simen1

      If you want to be taken seriously, try to be serious and factual. Do your math, do your practical comparisons.

  • Laslad

    His theories aside, what I noticed is a ignorance of the need to do certain online research before making that video, regarding the fact that (only) Sony, Olympus, Panasonic and Fuji cheated consumers.

    Canon EF-S 18-135mm is advertised as “Covering a range from 29mm-216mm in 35mm format”, but Canon did not tell us the f stop should be 5.6-9
    http://www.usa.canon.com/cusa/professional/products/lenses/ef_lens_lineup/lens_standard_pro/ef_s_18_135mm_f_3_5_5_6_is

    The same for:
    EF-S 10-22mm
    http://www.usa.canon.com/cusa/professional/products/lenses/ef_lens_lineup/lens_uw_pro/ef_s_10_22mm_f_3_5_4_5_usm

    EF-S 55-250mm II
    http://www.usa.canon.com/cusa/professional/products/lenses/ef_lens_lineup/lens_telezoom_pro/ef_s_55_250mm_f_4_5_6_is_ii

  • ronin

    Nonsense. Focal length and max aperture have remained a constant for measurement for well over a hundred years, across a variety of formats, from 4×5″ to 6×9 to 6×7 to 6×6 to 6×4.5 to 135 to 126 to APS to 16mm etc etc.

    Max aperture has been the primary determinent of light gathering ability, and hence names the lens speed.

    And yet, everyone has always known that while depth of field is constant for focal length/aperture, the apparent depth of field in an image changes with format.

    So a medium format camera with a normal field of view lens (~80mm/2.8 ) will have less depth of field for the same normal field of view from a 35mm lens (~50mm/2.8).

    How are the laws of optics a rip off? Why is providing the consumer with lens characteristics a rip off?

    • madmax

      Not very frequently agree your statements, but this time you are right.

  • Neil

    The presenter in the video, as I understand it, states that a given ISO for a full frame camera will be cleaner than on a cropped camera because it is able to receive more light. I’ve always thought that it depended on pixel size. So a FT 16 mp sensor will be noisier than a FF 16 mp sensor. But if that FF sensor was, say, 36 mp than the FF might be the same or noisier than the FF sensor? In other words, I thought it had to do with the signal to noise ratio per pixel?

    • Tony Northrup

      That’s a good question, and a common one. In this video I’m discussing total image noise, which isn’t related to per-pixel noise. Per-pixel noise requires you to factor in pixel density. Total image noise is the same whether you’re discussing a A7S or A7R, film, or your eyes.

  • Ibrahim Sultanem

    thanks,very informative…..obviously making a true 2.8 lens for small sensor then would be very costly and bulky
    no where will we see these lenses soon

  • Paulo Moreira

    Ronin says it all, well done! The presenter is a fraud, nobody is cheating nobody, the consumer just doesn’t care about learning technical stuff. By this order of ideas, medium format lenses should be supplied with a warning sticker: Caution, less depth od field than 35 mm, increased risk of innacurate focusing at full aperture, etc, etc.

    Never heard of this guy, but he his really an idiot, whay doesn’t he mention that you can’t have a shallow depth of field with P&S cameras? Those devilish manufacturers did not dare to go against the laws of optics and did not put a 50 mm lens on a tinny sensor as standard, better still, a 135/0.5 or something like that.

    He looks old enough to be from the film era, he is an insult to intelligence, presenting this matter as an exposée. By the way, do you know the faster your car goes, the harder you have to pull the brake pedal? I searched the manual of the car and they don’t mention it at all! The things we are kept from knowing! :)))

    • Tony Northrup

      I’ve heard the medium format argument a few times, and I’m not sure how it’s relevant, because camera manufacturers put everything in terms of 35mm and not medium format. However, all my math extends perfectly to medium format.

      And can’t we disagree and be polite? I make free educational videos on YouTube, so trust me, I deal with idiots every day. I always do it politely, however.

      • thedreamcast

        BTW, making free educational video is a marketing to sell your book or promote yourself like many photographers or other professions do.

        • Hubertus Bigend

          Right, but so what?

  • aa

    Um, don’t forget compacts. My canon s95 says f/2.0.

  • Moritz Wellner

    I could only go the first 5 min. There were so many mathematical errors inside there, that I couldn’t look any further… 18 x 1,5 = 24… seriously?
    There are videos that should get banned…

    • Tony Northrup

      That was a typo, and I did fix it with an annotation in the video. Sorry about that! It’s too bad you missed the entire video because of a typo, though. I think YouTube will be a pretty empty place if we start banning videos with typos :)

  • Andrew

    This critique of the video is completely false. If you are going to compare focal lengths in 35mm equivalent terms, you should also look at what that does to the f-number. Multiplying the focal length by the crop factor means that f-number DOES NOT apply to the multiplied focal length in either:
    – Noise equivalency
    OR – Depth of field

    Although the exposure settings don’t change. The noise equivalency can be verified simply by taking a large sample of SNR numbers from a site like DXO. Yes, the noise level of FF sensors is two stops lower at the same ISO, or the same at an ISO two stops higher. That’s because the ISO is computed to get the same exposure settings, not to provide the same noise level. A smaller sensor needs more gain to match the same ISO number as a larger sensor, hence more noise and is actually more sensitive at the same ISO than the larger sensor. Again, do the math and the science if you disagree, but it’s borne out in all the testing and benchmarks.

    This is borne out is every test and you can check for yourself.

    Also, f-number is computed based on focal length, so the 35mm equivalent focal length with the same f-number actually does have a larger aperture. Again, check the math.

    • thedreamcast

      Yes, in terms of smaller sensor has more noise, it is because the sensitive surface is smaller. We should not forget whatever size of sensor, if it is manufactured from the same manufacturer, resolution and the same process level, the PIXEL pitch and the micro lenses performance must be the same. That’s why higher pixel density has worse SNR and usually get more noise.

      • Tony Northrup

        Since you agree with what Andrew said, I’m just not sure what you disagree with in my video. You agree that multiplying the crop factor by the aperture gives you similar depth of field, right? And that also requires you to adjust the ISO to be equal in the way Andrew described? That’s really all I’m asserting.

        • thedreamcast

          Hi Tony, be open minded. I am not saying you are completely wrong. You have a good intention to educate people, but you need to review and edit your video.

          No, I don’t adjust the ISO, but I can adjust the shutter speed. When we shoot film, we can’t easily change ISO like digital, that what is the fast lens stand for.

          Companies didn’t lie to customers, if they multiply the F-number, it would mislead people that fast lens become slow. Also, I would say the shallow DoF is just side effect. When we intend to shoot macro or close-up by tele-lens, we have to stop down the F-number, right? Yeah, here, small format will get faster than FF. How come F-number needs to multiply crop-factor and mark it slower to confuse people?

          • Hubertus Bigend

            It’s all about which parameters you can change to get the most similar results. If you want the most similar results, you can’t change shutter speed, because then you will get a different motion blur. You can change ISO, though, and if you do, you will get similar image quality out of the sensor.

            Things aren’t different at all when stopping down to increase DoF. Let’s say you use a 50mm macro lens on FT and set it to f/11, the camera is set to ISO 200 and you expose for a 1/500s. To get the same image with a FF camera, you would need to use a 100mm macro lens, set it to f/22, shoot at ISO 800 and, again, with a 1/500s.

          • Andrew

            You’re still failing to look at all exposure settings together. You’re taking one or two settings, looking at them, and claiming that it doesn’t make sense while ignoring the fact that you have to look at the effect on all settings. Because of the area difference, the gain to get a particular ISO rating is higher with a smaller sensor. Scale everything together and you get equivalent results. It’s not perfect because of minor differences that arise from pixel pitch and other physical details, but those effects (according the benchmarks and real world tests) make a marginal difference, far less than a stop from MFT to FF. In real world tests, FF is between 1 and 2/3 stops and 2 and 1/3 stops better than MFT in ISO rating. That means that the area difference is an order of magnitude more significant than the architecture differences everyone is using to “prove” tony wrong. It’s right enough that you don’t have to care about the difference due to implementation details.

            I think it’s ridiculous that this is controversial since he demonstrated everything he claimed with real-world tests and you can go check professional benchmarks and realize he’s right. Most of us came to these conclusions years ago when we started working with smaller sensors. I don’t want to say it’s obvious, because obviously some people struggle with comprehending it, but it really is obvious when you look at all exposure parameters together.

  • thedreamcast

    Hello I just finished my work and come back to here.
    Someone understood what I am saying and someone doesn’t, anyway. Yes, this presenter surely nonsense. He breaks the optics rule and mislead people in his presentation, and incredibly so many people trust him, that’s why I share this video here.

    Manufacturers didn’t cheat us(but he did), the focal length equivalent is a reference for us to easily understand the field of view. 135 is the most common format across the century and we know them a lot, so that why we always use 135 equivalent as a standard.

    Why we don’t multiply the Aperture(F-number)? As what I said in my statement, it is just the photography principle. Aperture controls the light gathering and DoF is just secondary. It is shallow to regard the big aperture lens for background defocus. You must mention large aperture lenses are always called “FAST LENS”, not “SWEET BOKEH LENS”. “FAST” means the lens gives you fast shutter speed. In film age, it was a disaster if photographer doesn’t have a flash and HI-ISO film. That what is the FAST LENS for.

  • Andreas

    He is right, however, to get similar result, all 3 parameters have equivalent, there must be 35mm equivalent for mm, f and ISO. Doing so, you get similar angle of view, DOF, and noise. To be able to compare we should use all 3 equivalents, not only one and leaving the other 2 parameters, that’s the honest thing to do. A photo taken at 25mm f1.4 iso200 on m4/3 is equivalent to 50mm f2.8 iso800 on a FF camera (remember, it’s equivalent, not real 50mm f2.8 iso800).

    • thedreamcast

      You need to put 1 more parameter: Shutter speed.
      Anyway, your statement is logically correct but it is different to his. The difference is, we basically stop down aperture to get deeper DoF and better IQ, and we get this equivalent like your example, MFT users can get 2-stop lower ISO or 2-stop faster shutter speed. But he exchanged the concept, he think companies should multiply the F-numbers due to MFT is 2-Stop darker than FF(What?) refer to 31:20, he said Panny FZ200 can’t shoot sports photos @600mm equiv. because the equiv. f-stop is f/16 and f/16 is too dark to take sports pictures(WHAT!?!?!?)
      Oh man, he actually applied the wrong DoF equiv. to a small sensor camera!!!! Yep, this equiv. should have be applied to FF.

      • Andreas

        Shutter speed is the same
        25mm f1.4 iso200 1/200 on m4/3 = 50mm f2.8 iso800 1/200 on a FF
        25mm f1.4 iso200 1/100 on m4/3 = 50mm f2.8 iso800 1/100 on a FF
        etc

        • Mk.82

          For equivalent depth of field 35mm sensor gets two stops less light than m4/3 sensor.

          That’s why m4/3 gets two stops faster shutter speed in low light or two times lower ISO in low light. Or can use two times weaker flash or get two times faster flash recycle. Or can shoot from four times further with same flash power.

          Can carry two times more gear or get two times less weight and space requirements.
          Or can use two times less money to gear.

          All with same image quality, but improves handling, faster cameras, more keepers and having two times more fun without back pain as 35mm shooter.

          The m4/3 format is the ultimate and winner in everything compared to 35mm.

          And Tony Northrup can’t stand it (being 35mm brainwashed) and does everything in his power to stop truth spreading out making photographers life’s easier, by lying and inventing his own evangelism and telling it in own videos.

  • J Shin

    Well, he must be right, ’cause he has an Internet video! He sure sounds like someone who knows exactly what aperture values mean and how it effects the image capturing process, like exposure. And he seems untouched by the evils of neutral-density filters.

    So, by this logic, medium format manufacturers are reverse-cheating us, by overstating their aperture equivalents? Conversely, no wonder I never felt comfortable with my 6×9; I thought I would get fantastic depth of field at f/5.6, but it was really f/2.2 equivalent, with barely anything in focus, unsuitable for landscape! I just stayed away from 8×10 because of all this cheating, of course.

    And Leica should be added to the bad list, since they never bothered to mark any kind of equivalents on their lenses when M8 and R9-DMR were their flagships, and so all their lenses were crop lenses. In fact, when they doubled the image size with the Leica I, they should have stated the correct cine-35mm equivalent in the first place. Like, say, Voigtländer does, according to this guy. Right.

    By the way, shouldn’t FE lenses come with µ43-equivalent apertures marked on the lens barrel, since, you know, µ43 is the first and more established mirrorless standard?

    And don’t Canon and Nikon sell more compacts with “cheating” apertures than anyone else? I have a Demi S sitting in my closet that clearly has the “cheating” aperture marked on it. Canon’s been cheating at least since 1964!

    Who can we trust now?!

    • J Shin

      I just realized my Leica R 28/2.8 lens is cheating me, too! It should really be marked f/0.88, since that is the DOF-equivalent aperture to 50mm lens! Those fiends! I can’t believe I gave my money to Leica instead of Nikon, who clearly are too honest to keep up with the competition!

      http://nikonrumors.com/2014/05/17/nikon-misses-financial-forecast-stock-down-at-3-years-low-company-restructuring-announced.aspx/#comments

    • thedreamcast

      I always get into trouble with lack of high ISO film for my Bronica ETR 645. I never knew my boy is outstanding fast like a Ferrari!! I am surprised

    • Andreas

      To use an equivalent is useful, so users can easily know what will get.
      The FF frame 35mm or 135 format is used for equivalents values because it was the most used. All the compact cameras and video-cameras use that equivalent.

      Also to have to have the equivalent on all 3 parameters (mm, f, iso) is very useful. You can get answers like, “what mm to use for a landscape?”, “what mm to use for a portait?”, “what f to use for a portait?”, “at what f value does the diffraction starts?”,”what is the maximum iso to get a nice quality (noise) for an A3 print?” etc.

      • Mk.82

        On last decade most used was Half-Frame, as known today as APS-C. That is the factor what needs to be used with DSLR and mirrored.

        M4/3 is 1.5x and 35mm is 0.75x.

        But last 5 years there has came the other format to rule.
        1/1.8 or even 1/2.3″ what is the most common for smart phones.

        In one year there is only 1.7 million DSLR sold, same time there are ten’s of millions phones sold with a camera.
        And people are custom to see their focal length is 4.2mm or 5.1mm and so on.

    • Tony Northrup

      This argument comes up regularly, but nobody puts anything in medium format terms, which is why I don’t bring it up. But I do shoot medium format regularly.

      • Mk.82

        Yes they put, everytime people talk about differences between 35mm and 50mm or f/2.8 vs f/3.5 they bring it up.

        You lied, you didn’t mention factors YOU changed to make your lie fly and you can’t stand you would be required to withdraw your false information videos what hurts consumers.

        You don’t understand that “crop factor” is known as “focal length multiplier” by master photographers. And it is used only when identical angle of view is wanted to be achieved between formats, why it has as well the synonymous term “format factor” and 35mm (what is BTW the Small Format aka Crop Format, not a full frame) is not the standard as uneducated people believe it is.

        Small Format is only used as example by manufacturers because people are searching lenses to get the identical angle of view, why they need to know the focal length multiplier factor so they know what focal length they need to get same angle of view.

        Those who can’t, teaches.

  • Jacques_F

    He maybe triyng to be right, but definitely tells unacceptable conclusions, by misleading people accusing Mirrorless manufacterers as bad boys cheating people, and presenting Canikon as the only good boys !
    All manufacturers are doing the same in their advertising, including Canon, since APS-C was introduced,
    like in Canon G1X MK2 specs as below:
    http://www.usa.canon.com/cusa/consumer/products/cameras/digital_cameras/powershot_g1_x_mark_ii#Specifications
    where it is simply mentionned:
    Focal Length: 12.5mm (W) – 62.5mm (T) (35mm film equivalent: 24-120mm)
    Maximum Aperture: f/2.0 (W), f/3.9 (T).

    They also don’t mention crop factor equivalence !!!!!!
    Is he paid by Canikon to lie on Mirrorless companies? HE is cheating people !

    • Laslad

      IMO this act by Tony is alot worse than (possibly) misunderstanding and/or misstating the theory, and people who defend him simply ignore it.

    • Tony Northrup

      I do retract the part about Canikon being good guys–they’re not as obvious about it, but helpful viewers found some examples of them doing the same trickery. I amended the video and updated the title.

      Nobody paid me.

  • Hubertus Bigend

    Ale is wrong, Tony Northrup is right.

    “The Panasonic 12-5mm f/2.8 has a f/2.8 aperture and not a f/5.6 aperture.”

    Right, but Tony Northrup never said otherwise.

    “You don’t have to make the equivalence he says has to be done!”

    Right, you don’t have to, but if you do, and if you start constructing a hypothetical equvalent lens with an equivalent focal length, then you have to calculate the equivalent aperture, too, otherwise that hypothetical lens is NOT equivalent.

    “Use the Sony A7r and Sony A6000 for the same shoot. To get same result the camera automatically sets on both the same ISO and same lens aperture despite the different sensor size.”

    Wrong. You don’t get the same result by using the same ISO on sensors of different sizes. Try it with a 1/2.3″ vs. a Full Frame 35mm sensor and you immediately see what I mean. The results won’t be equivalent, because the much smaller sensor gathers much less light at the same F-Stop, resulting in massively worse image quality. Only if the smaller sensor is used with less ISO, as far as that’s possible, the result will become comparable, will become equivalent.

    And just because the difference between FT and APS-C and FF isn’t that big it doesn’t mean the maths and the physics behind the principle aren’t valid. They are, and they stay the same.

    • Ale, MR Admin

      Hubertus you made the same mistake as Tony!!!!
      1) Hypothetical equivalence cannot be done on “focal length” but on “field view”. Focal length is FIXED.
      2) APS-C vs FF test: Again, you didn’t get it. The settings the camera give you are equal! But of course the FF handles nosie better because of the much larger area (assuming both sensors have same total pixel ammount).

      Hubertus. Please read Wikipedia article about crop factor to learn the physicis, maths and variable to take into consideration: http://en.wikipedia.org/wiki/Crop_factor

      • Ale, MR Admin

        The first part of the video is correct. On paper a FF sensor at ISO 1600 has the same noise level of a MFT sensor at ISO 400. That’s the only part were he is right :)

        • theSUBVERSIVE

          And it’s only on paper as well, it’s only true if the EXACT same tech in used on the different sensors, which is not really the case most of the time.

          • Hubertus Bigend

            Yes, but what else should be considered equivalent if not that which comes out of a camera if and when the same level of tech is used?

        • Brauni

          You somehow missed the part in that link you posted where he writes: ” It’d be the same if every full frame photographer heard that their 24mm f/1.4 was really ‘only’ equivalent to a 180mm f/11 on an 8×10 view camera. Yes, that would be the ‘equivalent’ lens in focal length and aperture for the same depth of field, but who cares?”

          Tony is absolutely right. When Panasonic prints 600mm f/2.8 on a small camera lens it is simply a scam!
          They can print 600mm on it OR f/2.8 BUT NOT 600mm f/2.8.

          • Andreas

            600mm f/2.8 means that the aperture has a diameter of 600/2.8 = 214mm. 214mm is enormous. Saying that your small lens is like a 600mm f2.8 is crazy.

          • Tony Northrup

            Just to provide a visual example, here’s a true 500mm f/2.8: http://www.fredmiranda.com/forum/topic/881981

            I wish I’d thought to put that in the video :)

        • Bhima Jenkins

          Even that is somewhat misleading because it depends on the FF sensor you are talking about. Obviously a new Nikon FF is basically amazing when it comes to noise.But an EM-10 actually has better noise levels than either the FF sensors in both the Canon 5D1 and 5D2 and is actually competitive with the great APS-C Nikon D7000 (check the RAW graph for yourself):
          http://www.dpreview.com/reviews/olympus-om-d-e-m10/12

          It also has better Dynamic Range than either the 5D1 or 5D2. So… while I understand the academics of pixel size, it doesn’t always seem to play out in these tests, nor in photographs.

        • madmax

          On paper…

      • Hubertus Bigend

        1: Does not make sense. If you want the same results on two different formats, one of the parameters indeed is the field of view. But the field of view needs to be identical, not just equivalent. And to get the same field of view on another format, you need to use equivalent focal length, which is the original format’s focal length multiplied by the crop factor between both formats.

        2: The cameras can give you whatever settings they want, that does not make the results similar. To get images which look the same, you need to use equivalent focal length, equivalent ISO, and the same shutter speed. It really is as easy as that.

        People who tell otherwise try to defy physics and try to defy what everyone can see for themselves by shooting and comparing their gear, even if they don’t want to believe in physics. I call that pure ideology. Or call it religion, if you like that better.

  • Jacques_F

    @ Admin: your corrections are OK, but Tony Northrup is a DANGEROUS guy.
    I could conclude as you “I know Tony had good intentions” BUT if you follow the full video what is UNACCEPTABLE is that he is ACCUSING Mirroless manufacterers marketting are lying and misleading by CHEATING PEOPLE with false advertising while HE IS WRONG HIMSELF and without double checking what he is stating !
    in that way he is dangerous !

    • Ale, MR Admin

      Tony is absolutely a nice guy! The equivalence debate is many years old and many people keep doing mistakes.

      • Jacques_F

        OK he is a nice guy …. who is saying during 20 minutes from 21:18 to the end that Mirrorless companies are LYING ! with many examples as:
        Panasonic misleading, Olympus misleading, Sony misleading with many product shown (Lumix 12-35mm, FZ200, Olympus Stylus1, Sony RX10, etc…) each time saying these companies are doing bad advertising (bas boys) TRICKING consumers (Tony’s words) and presenting Canon, Nikon as good boys,
        and as a conclusion of the video, he shows and insist on a slide telling:
        “YOU (each of us)
        Convert both Focal Length & Aperture
        Politely remind people who forget
        Educate others & share this video”

        He seems to have found a kind of (false) mission of evangelism. that’s dangerous anyway !

        The first part of the video he calls TUTORIAL is educational, so even he is doing mistakes we don’t care, but the secong part is ACCUSATION to companies and that we cannot accept !

        • Tony Northrup

          For the record, after viewers found examples of Canon, Nikon, and Fuji doing the same trickery, I extended it to those companies… though the examples I cite in the video are still far worse.

          • Laslad

            You have left out (literally) almost every other lens manufacturer in the title, for example Leica (Leica T), Pentax, Ricoh, Sigma, Tamron, the list goes on and on.

            If your intention is to warn customers of the wrong information advertised by manufacturers, then cheating is cheating, there is no such thing as a matter of degree. Well, I guess you couldn’t care less, after all you are just trying to sell your book and all you care is how good it sells..

    • Tony Northrup

      Well, I did take a free karate lesson as a kid.

      Did you watch the entire video? What exactly was wrong?

      • Jacques_F

        Mr Tony Northrup: you call your video “TUTORIAL” but it is not only educational, it is also controversal only against some companies, and that is not fair at all.
        You should have presented your video without accusing some companies as bad boys and other as good boys. All companies including Canon, Nikon are doing the same (PLEASE look at the Canon web site link below).
        THAT’s IT and if you don’t want to recognize it, you are unfair and not clever !

        Canon G1X MKII specs: http://www.usa.canon.com/cusa/consumer/products/cameras/digital_cameras/powershot_g1_x_mark_ii#Specifications

  • darrask

    Gosh, so much confusion here… so many people simply don’t get what equivalence means and become emotional.
    Equivalence is not equality, equivalence means “same value”.

    • thedreamcast

      Yeah, good, “same value”

      When we are talking Focal-length equivalence, normally talking about equivalent FoV, JUST because people always use Focal length as FoV reference. As well as when we are talking Aperture, normally talking about controling the amount of light, just like our pupil, we don’t use it to control the DoF.

      So companies don’t need to multiply F-number then say “equivalence”, because the F value is no the same.

  • theSUBVERSIVE

    Aperture is Aperture, DOF is DOF, FOV is FOV.

    Aperture is not measured in depth, FOV is not measured in how much light it captures, just as DOF is not measured in how much of the scene you can see.

    Aperture indicates how much light goes in, FOV indicates of angle of viewing, while DOF, as it says, indicates the depth os what is in focus.

    Why would a manufacture need to sell on equivalent measures rather than the real measure? a 12-35mm may be equivalent to a 24-70mm FF, but it’s still measures 12-35mm. I think that if anyone gets tricked down by this natsayers and base their photography or video on that, they deserve to live by this belief. There wukk always be the ones that say that FF is PRO and all sort of limited minded thinking.

    • Tony Northrup

      I’ve seen the “caveat emptor” argument many times, and that’s the biggest reason I made the video–to educate people so they can make better buying decisions. If you watch the samples reviews I read, people really don’t understand. In the last couple of days since I posted the video, I’ve gotten a lot of messages from people who spent thousands on gear after being mislead by manufacturers.

      I understand caveat emptor, and the buyer always has some responsibility, but this is a really technically complex topic and even many technically-savvy photographers don’t seem to understand it.

  • Olivier Duong

    Thank goodness, since I’m a simpleton I focus on making photographs :)

  • Mireille Marivoet

    A 12 -35 2.8 is not a 24-70 5.6, it is and will always be a 12-35 2.8.
    He states that he could not find nikon, canon or Fuji cheating??? Didn’t look very hard did he, took me 1 minute to find the same ‘misleading data’ on the official canon site:-)

    I do think that most companies oversimplify, and that it should be taken with a grain (bucket) of salt, but hey these are marketing guys, bring on the truckloads of salt (who ever believed the white smile toothpaste commercials :-)

    • Hubertus Bigend

      “A 12-35 2.8 is not a 24-70 5.6, it is and will always be a 12-35 2.8” – yes, but if you want the most similar FF lens to a 12-35/2.8 MFT lens that will ever be possible to make, meaning the lens that will give you the most similar options and results, you’d have to get a 24-70/5.6, and that’s what everything’s about when a manufacturer starts telling us, hey, this lens is equivalent to a 24-70 zoom on a full-frame camera. And while they are of course right in saying so, they would be wrong in suggesting that it was equivalent to a 24-70/2.8 zoom on a full-frame camera, because, as the video explains and proves, it isn’t. Which, by the way, is all the video is about. I don’t understand why it takes more than half an hour to explain, though.

    • Tony Northrup

      Note that I did amend the video and the title to include Nikon, Canon, and Fuji in the cheating…. but they’re not nearly as awful as the examples I cite in the video. But viewers found good examples after I recorded the video, and I’m always happy to correct an oversight when I make one.

      Mildly interesting: Nikon abuses this technique *seriously bad* in every country I could find except the US. If you check, say, the NZ website and the US website, they abuse this technique obviously in NZ but very subtly in the US.

  • hexx

    i stand corrected – this video is utter nonsense

  • Aaron Weiss

    Someone needs to remind Tony that a lens is a lens is a lens. f/2.8 is f/2.8. https://www.youtube.com/watch?v=ZF4GSMw1CeQ

    • Tony Northrup

      Heya, Aaron. Give the video a full watch… the resulting image created by f/2.8 changes quite a bit with different sensors. Thanks!

  • J Shin

    Ultimately we are all talking/arguing about conventions. The F-stop value is not even a good measure of how much light reaches the sensor; that would be the T-stop. The focal length marked on the lens is never the exact focal length of the lens; with internal focusing, in fact, the focal length changes as you focus. ISO values for digital sensors are not standardized like it was for film, and some would argue that it was a poor guideline and highly subjective even for film, and it of course varied with development; so, ISO values of digital sensors are basically “equivalents” to film ISO, as each manufacturer sees it. If you dig into it, none of these concepts really mean what they usually are taken to mean. Conventions are just shorthands for complex ideas. We could say “sensor sensitivity to light, equivalent to ISO-5800 film sensitivity standard, measured by one of the methods specified in ISO-12232, i.e., after the raw image has been output to sRGB format per manufacturer discretion”, but we just say “ISO”.

    In the end, most of us know what the facts are. FOV, DOF, EV, focal point, DR, FL, F, T, ISO, shutter speed, … they vary with one another, and we know the formulae for how they vary. We are just discussing what to call these phenomena, and which phenomenon is more important in what situations. Within these discussions, over time, certain conventions arise, and conventions are, by nature, arbitrary.

    Why is mint green called mint green when it looks nothing like mint? Why are we still calling 735W “one horsepower”, when that is not the typical output of any horse? Why, oh why, is anyone still using candlepower? Why are vertical frame orientation called portrait? Who cares? As long as we vaguely understand each other, conventions will persist, and they will be arbitrary, and always “cheat” to a degree. We just need to remember to use more precise language when it matters.

    I know… we’ll never stop having this argument. Some day in the distant future, when all the FF and APS lines have died off, we’ll be arguing about m43 vs. 1/2.33″ sensors, which, by the way, are not 1/2.33″ in ANY dimension.

    • Hubertus Bigend

      It’s not at all about conventions, it’s strictly about relations. No matter how we name or measure apertures and sensitivities, the relations between the underlying mathematical, geometrical and physical quantities when comparing sensors of different sizes will always stay the same. Which in itself is a mathematical and physical principle. It’s those relations which define equivalence. And Tony Northrups video shows what those relations look like within the parameters of what we most commonly use for measuring those quantities today.

      • J Shin

        You raise a very important point.

        > It’s those relations which define equivalence.

        Yes, exactly, but only under certain conventionally defined conditions. When we are talking about DOF, “equivalent aperture” should be multiplied by the crop factor; Tony is right. When we are talking about exposure and dimensions of the effective aperture, however, it shouldn’t be.

        “Circle of confusion” that defines DOF is itself a conventionally defined “parameter”, loosely based on average human visual acuity at average viewing distance and enlargement size. 1/100″ or 0.254mm for large format, 1/30mm for 35mm, 1/60mm for m43. Equivalent DOF is thus–conventionally, and, I’ll add, sensibly–defined for when comparing two final prints of the same dimensions, rather than, for instance, at the same magnification. DOF is also measured–again, sensibly and conventionally–at the object plane rather than, for instance, at the image plane; if latter had been the convention, we would be saying that all lenses with the same f-stop have the same depth of field!

        Furthermore, the effective optical aperture of a lens changes from center to corner because of the slant of the light; therefore, so do DOF and EV, even more so in the far corner because of vignetting, sometimes up to 2 stops, but this is pronounced only when the aperture blades are wide open! Never mind that the shape of the aperture changes as we move to the corners, so the idea of “diameter” used in f-stop and t-stop measurements is a small misnomer.

        On internal focusing lenses, the f-stop value changes as the focus changes, since the focal length changes. Focal length change, in fact, has a far greater proportional effect on DOF; an internal-focus lens that is 50mm/4 at infinity, when focused to typical maximum magnification of 1:10, will have a 45mm focal length, and have aperture of f/3.6. So, is it an f/4 lens or an f/3.6 lens? Convention says f/4, and that’s how the lens comes labeled. Good-old barrel-focused lenses, of course, will not have this “relations”, but, with them, FOV changes with focusing; at closer distance, you end up with a narrower-angle lens, and lose exposure to boot, but, guess what, the DOF does not change because conventional calculations of DOF assume barrel-focusing, not internal focusing! So, are we being cheated out of the FOV by using internal-focused lenses? Or with barrel-focused lenses? Mostly, we ignore this whenever we pull out our handy-dandy DOF calculator. (What do you mean you don’t have one? What about a DOF target? Everyone should have one, don’t you think?)

        Another factor that needs to be ignored is that DOF is calculated at a certain sensor-to-object distance. On smaller sensors, less portion of this distance is taken up by the lens’s optical length. That means that the FF DOF at 50mm/4 is NOT exactly the same as m43 DOF at 25mm/2 at the same focusing distance; in fact, m43 will have slightly greater DOF, because it is focusing at a slightly farther distance from the optical center. A better way to measure focusing distance, therefore, would be that between front optical center and the object; if you do the math, then and only then FF DOF at 50mm/4 will be exactly “equivalent” to m43 DOF at 25mm/2. This is, actually, a better way to measure distance in the first place, since it’ll make a lot of calculations much simpler, and it’s easier to hold a tape measure on the barrel of the lens, closer to the optical center, than on the top plate of the camera. (Does your camera even have the sensor plane marker?) Distance will also then be directly proportional to magnification, and we can then compare DOF at same equivalent magnification, such as 1:100 for FF and 1:200 for m43. So, is anyone going to clamor for this change? Nope. Convention rules!

        And, of course, many Canon “full-frame” sensors are smaller than 24×36, resulting in DOF-cheating, per Tony. Who is cheating now?

        And who decided that 24×36 is “full frame”?

        So, should aperture be measured in the center? In the corner? At infinity? At 100m? At 100:1 equivalent? Using actual measurements or using barrel-focusing equivalents? And what is the margin of error? Is DxOMark going to measure the actual effective apertures of all available lenses to tell us with which lens we can eke out a little more FOV or DOF or exposure? Well, yes, in terms of exposure, they do measure the t-stop value. Yay. Using the conventions of the cine world, of course, where exposure equivalence matters A LOT more than DOF equivalence. (You can’t use t-stops to calculate DOF equivalence, although you can approximate it, much as you can approximate exposure equivalence using f-stops…)

        Yes, the underlying physics is the same no matter what we call the variables, but there is nothing objective about the word “equivalent.” I’m not saying that Tony’s basic arguments are wrong. I’m taking issue with the idea that somehow there is a “good” convention of labeling things and a “cheating” convention. They are all dubious conventions we like well enough.

        Just like the m43 standard. :-)

        • Hubertus Bigend

          While your comments on the dubiousness of the conventions concerning how we measure some, if not all, of those variables are perfectly valid and while that is a very interesting subject by itself indeed, it does not affect the maths and physics of equivalence in a way that would invalidate the general rule of equivalence Tony (like many others) states.

          The relation which defines equivalence stays exactly the same however dubious our conventions in specifying the variables are. Because almost all of those variables cancel themselves out in the relation, while the remaining one or two, even if dubious from an exact physical perspective as we specify and measure them, are a good enough approximation for real-world photographic applications as they are conventionally used.

          We all know that there is no such thing as an ideal lens. So of course the equivalence rule must be implicitly read like this: If you have a 40/1.4 MFT (e.g.) lens and want to know what kind of lens would be needed on a technically similarly advanced FF camera to provide the most similar bandwidth of options and to produce the most similar kinds of images, it would be an 80/2.8 lens *of otherwise similar characteristics*, used at quadruple ISO.

          When manufacturers tell us, the 40/1.4 MFT lens is equivalent to an 80mm FF lens, that’s perfectly true (and still sufficiently true for some Canon sensors that do not quite measure 36×24). But is that all? Is it really equivalent to an 80/1.4 FF lens? No, because with an 80/1.4 lens on FF you will always be able to take pictures you cannot ever take with a 40/1.4 MFT lens. So there’s no way to claim THAT definition of equivalence was right, if what real photographic images will look like in practice in under the same external shooting conditions is what we’re interested in. If we’re not, the whole question of equivalence would be moot in the first place. But what is the right definition of equivalence? Tony and many others including myself know, the simple geometrically defined rule Tony explains and proves in his video is the one, because it defines best with which lens-camera-setups we will get the most similar photographic options and produce the most similar looking photographs.

          If anyone defies this assumption, I think they should come up with an even better rule of equivalence and prove that it works better in defining with which lens-camera-setups across different sensor sizes we will get the most similar photographic options and produce the most similar looking photographs. And it is perfectly valid to call a rule “good” which is, indeed, good at that, and to call one “bad” which fails in appropriately specifying those setups.

          • J Shin

            > it does not affect the maths and physics of equivalence in a way that would invalidate the general rule of equivalence Tony (like many others) states

            I’ll just repeat myself. I agree with you; I do not dispute that.

            Also, if you watch the video, he does not specifically discuss the physics they way you do. He does misstate some concepts, although he is not wrong, exactly; others have discussed this, so I’m leaving this here.

  • yakisobskie

    had 1 question for the critique of the video.

    aperture forumula is Focal Length / Diameter. How come the aperture never changes when the focal length changes on different sensor sizes?

    you’re argument seems to start saying ISO is the absolute truth. his argument starts saying ISO is a useless information. can’t compare both your conclusion since you two are making different assumptions to begin with.

    • Hubertus Bigend

      Fact is, image quality as far as it is limited by the sensor tends to be equivalent between two formats when the ISO setting of the larger format is multiplied according to the crop factor between the formats (i.e. multiplied by crop factor squared). That’s per theory, if you accept the rule that, under normal circumstances, image quality gets the better the more photons make up the image, and it is the empirical result of real-world comparisons between existing sensors of different sizes and of a similar technological level. So, yes, in order to choose parameters which are supposed to lead to the most similar and the most comparable results, i.e. equivalent results, ISO has to be adjusted for equivalence, too.

      • Tony Northrup

        Yay for this discussion, and thanks for watching the video!

  • Pat

    I think Tony makes it pretty clear that he is calculating for total light collected by the sensor.

    Yes, an f/2.8 lens is and f/2.8 lens, but that’s not the point. Aperture is a function of focal length, so if you change the focal length you are changing the size of the aperture. The 12-35 will give the same FoV as the 24-70, but even if they are both f/2.8 they are not equivalent lenses when it comes to the quantity of light they transmit to the sensor.

    Tony is correct in pointing out that manufacturers are quick to advertise focal length equivalence, but not aperture equivalence. I’m kinda shocked so many people got their panties all twisted up over this.

    • Tony Northrup

      Thanks for that reply! I really can’t say it any better.

      I also have *no* idea why people are so mad about this. It’s pictures and cameras, it’s fun stuff!

    • Ale, MR Admin

      Wrong Pat. Tony is bvioulsy right when saying TOTAL light with same aperture is (on paper) 4 times larger on a FF sensors vs MFT sensor. But that’s not the point. It’s simly a deep logical error to say the lens aperture has to be multiplied and that companies are cheating.

      • Pat

        There is no “deep logical flaw” about it. If you are going to multiply focal length by the crop factor then you should apply that same to the aperture. The aperture is a function of focal length by definition.

        If companies are going to advertise equivalency then they should apply it to both. The maximum diameter of the diaphragm on a 24-70 F/2.8 is twice as large as the maximum diameter of the diaphragm on the 12-35 f/2.8. Or not advertise equivalency at all. Just advertise the lens for what it is.

        • Terry Yu

          yeah but the problem is EVERY company does it and his video makes it seem like the DSLRs don’t apply whereas, since everything is in 35mm terms, all cameras that aren’t “full-frame” fall under this category. People that don’t know any better and just take his word for it are being even more misled.

          Canon S110 is what, a 24-120mm…oh wait, but that’s Canon blatantly lying about the aperture being f2.0! Which company doesn’t do this? If anything, he should try to educate people on what the difference is between focal length and field of view and equivalent instead of saying there are these BAD companies and then these good companies (and then add in a little note saying they are bad too, just not as bad).

          • Twins Nesta

            And Tony never answer this both on youtube and here

          • Hubertus Bigend

            Actually, he did several times here, where he states that he stands corrected and that he’s indeed added Canon and Nikon to the list of culprits.

      • madmax

        I think you this time made a mistake. Your statement is true only when you are comparing “equivalent” focal lenghts. A 200 mm f/2.8 lens for 4/3 and a 200 mm lens for FF gather roughly the same amount of light. This amount of light depends on focal lenght and f number.

  • Hubertus Bigend

    Anyone who’s interested in insight, try to answer a simple question for themselves.

    Assume you have a 45mm f/1.2 lens on a Micro Four Thirds camera.

    Assume further that you get the job to design and produce a lens for a (technologically similarly advanced) Full Frame camera, so that the lens will offer as similar a bandwidth of photographic options as possible, not more and not less, and produce pictures which will look as similar as technically possible in every respect under the same external circumstances.

    What do you come up with?

  • Cristiano

    Hi everybody,
    This seems to be not a forum for photo enthusiast, but a scientist symposium!
    The point is that nowadays many people think that buying a 4/3 with a 2.8 24-70 “35 millimetre equivalent” will get the same result as the guy that is holding a full frame camera with a 24-70 2.8.
    He explained very well that this is not true, at least now you will understand why the result with your mirror less will be quite different from a full frame.
    No one is saying that mirror less are not great cameras, but producer should be more transparent, and buyer should be more informed about what they are buying . Assuming that buyers have the right understanding that the result “will not be equivalent to a 24-70 2.8 on a 35 mm camera” everybody is fine!

  • Tony Northrup

    The guy in the video here, let me address some common comments:

    * I know it’s long, but please do watch the entire video before accusing me of being wrong.

    * With that said, I do have a few minor corrections that I made with YouTube annotations (which might not be displayed on all clients): 18mm should have been 16mm on one of the slides (and there was another typo that I forget), and Canon, Nikon, & Fuji have also abused crop factor… but not quite as blatantly. Oh, I use ‘bokeh’ very casually, and I’m aware of the technical definition, but you know what I meant, and that’s what counts. To the best of my knowledge, those are my only mistakes, and I’ve done my best to verify hundreds of comments.

    * If you read the Admiring Light article, and watch my entire video, you’ll see that we totally agree with each other… to such an extent that I feel like I have to say I didn’t see the Admiring Light article before making my video. I did my own primary research and came to the same conclusions. Note that the article goes into detail about how sensor technologies differ, and my video is a bit more theoretical, but I specifically say, “given similar sensor technology” to address the concern. If you think this article disagrees with my video in a fundamental way, than you probably misunderstood one of us.

    * The Mirrorless Rumors admin says that if you get the same brightness photo using the same settings on two cameras with different sized sensors, than it proves I’m wrong. I think this just proves that he didn’t watch my video, because I actually show the results of that exact test multiple times (and of course the brightness is the same). The fact that those settings produce images with the same brightness is the basis for my entire argument.

    * I’m not discussing per-pixel noise, I’m discussing per-image noise. An A7R and A7S both have the same per-image noise, as will film or your eye. Different pixel densities will yield different per-pixel noise, yes, but that’s simply not the topic of the video. At several people’s request, I am planning a video to discuss the merits of pixel density. It’s an interesting subject; it’s just a different subject.

    * The “35mm camera makers are cheating us because of something with medium format” argument: Nobody labels non-medium format lenses with medium-format equivalents. My math holds true for medium format systems, which have a crop factor < 1. I'll check back and I'm happy to answer any questions! Thanks for watching!

    • Twins Nesta

      So I still think that you should amend the video title and add Canon and Nikon and some other brands. They are absolutely doing the same and no less as you say. You say on here with one sentence to defend Canon, Nikon but mislead people only Panasonic, Olympus, Sony cheating people on the whole video. I think you are doing some misleading

    • Ale, MR Admin

      Please Tony. Talk with an optical expert. He wille xplain you what’s wrong with your equivalence calc. I think it’s the best because we get lost in endless discussion. Note that on WIkipedia itself you will find the basic rules about crop factro and field of view. Crop factor has no influence on the aperture (which is fixed).

      • Hubertus Bigend

        He never claimed a lens would physically change aperture by attaching it to a differently sized sensor. (Have a look at my comment on your “Canon guys can make a simple test” post.) But if you use it on a smaller-sized sensor, it will give you images which look very much as if you would have used a longer focal length with a slower aperture on a larger-sized sensor with accordingly adjusted ISO.

    • J Shin

      Hi! Well, congratulations on your thought-provoking, informative video. As they say, there is no such thing as bad publicity! :-)

      I’ve just read through your responses to this thread, and I noticed that you are mainly responding to technical challenges to your points. I don’t have issues with your technical points, but there are two important things for you to know, and that others have addressed:

      1) The whole aperture equivalent argument is a giant hornet’s nest. You make a (potentially/factually) valid point, but there are a lot of hurt feelings among us small-sensor fans because this is the topic most frequently abused by trolls and people slumming from the FF DSLR world. I’m Asian-American, so I’ll give you an Asian equivalent: it’s may seem fine for someone to point out that Asians are overrepresented in technical fields in the US, because it is factually true, but when day after day you run into people who point this out to you, this becomes oppressive. As a woman, I’ll give you a woman’s world equivalent: it may seem fine for someone to point out that I’m wearing a nice outfit, but when day after day that’s all people point out, it becomes unbearable. That’s how hostile environments are created. So, be kind to our cultural sensitivities, and just back off this topic here. If you don’t, many of us will respond to you as we respond to trolls, as have I, below. (Sorry!) Besides, most of us have come to realize that awareness of dynamic range and equivalents get us only so far, artistically speaking, and consider much more than technical definitions of image quality in selecting our gear. I realize you weren’t really talking to us, but, for here, let us be.

      2) Education is great, and welcome. But, accusations are uncool; calling these things “abuse” or “cheating” is a bit too much, as is “feeling bad” for someone who may have made an informed choice. It’s your tone, I think, that most people here object to. Being right is welcome, but only when packaged with some humility. I admit I don’t practice what I preach in this regard, but, as they say, those who can’t, teach, and those who can’t teach, become pundits. Consider adopting a tone less like Ted Talks, and more like, say, Carl Sagan. Less like Ted Cruz, more like David Brooks. Especially since you are touching on some controversial topics, you need to sound like someone who is aware of the controversy.

      The Panasonic bit starting around 22:15 is the case in point for both my critiques here. You are making a valid point, but the way you use the word “equivalent” and “feeling bad” for people who “don’t know”, etc., makes you come across as pretty sloppy and self-satisfied. I actually couldn’t understand your argument, first time through, even knowing what you were trying to say. Your math works, but your explanation of how that should be reflected in the size and the price really didn’t make sense because of the glib way you put it, and makes it seem like a slight-of-hand; I guess one could say that, in a way, it was, because you do end up misrepresenting what aperture value means. I do suspect you are not entirely familiar with the concepts you describe; I could be wrong, but that’s how you came across.

      Well, hope this helps.

  • Joaquim Herrera

    The video “point of view” is absolutely correct….if you don’t agree, please try to shot stars or deep space objects with a small sensor and regular lens and you get the question of the rain bucket very kickly!! Astrofotography is done with small sensor, but please look at the size of the telescopes and the time of exposition. It’s so simple to understand….come on!!!

  • Swan Sany

    The point he is making in the video is ,by super imposing FF camera and lens shadow on a MFT or APSC body and showing it on the website clearly states that the manufacturer wants customers to believe that those are the same.And we know that in numbers they may be same but they cannot produce similar results in various conditions.

  • Richard James

    I don’t think tony ever said that a different sensor magically changes the lens. Yeah a 100/2.0 lens is a 100/2.0 no matter what sensor it is using it. However if we take a picture at the same location with that lens fully open on a FF it is a totally different picture you get using the same lens with the same settings on a cropped sensor. That’s the whole point. That is why companies put the 35mm equivalent on lenses that are made for cropped sensors because the image you get is different due to a smaller field of view. The field of view is what matters

    Now lets look at this scenario in 2 ways: First we could move closer with the FF and get the same composition as we got with the cropped sensor, once we do that we get 2 different images, as tony shows on the video and you can test it out for yourself.
    The second thing is we could move away from the subject with the cropped sensor to get the same composition as you got with the FF the effect would be the same as the first case.

    The subject will be closer to the FF camera no matter what you do, thus the DOF will be shallower and we will have more background isolation, if we want to get the same composition with the same background isolation on a cropped frame from the same distance as the FF we need a faster lens. Again that’s the whole point and just as manufacturers convert the focal length because we have a different field of view ( which is the actual relevant part not the focal length) we also get a different DOF. The final product is different even though on both cases you using pretty much the same lens on the same settings.

    Now if you are making a lens specifically for a cropped sensor format, why don’t you indicate this ? IMO it is pure marketing and I think it is quite a bit dishonest.

    “After re-watching the video I am sure Tony confused “Focal length” with “Field of view” ! ” Not quite. The focal length is used to determine the field of view its basic geometry , the Field of view depends on 2 factors the focal length and the sensor size. That is another reason why they say the equivalent 35mm focal length so you know what the field of view is.

    He also clearly states that he is changing the focal length to adjust for the change of field of view. I agree with you that regarding the physical aspect of the lens that is not possible.However if we are talking equivalency then that’s completely valid. A picture taken with the same FOV with the lens on the same settings with 2 different sensors sizes will have a different DOF. we also know that the amount of light getting to the cropped sensor is not the same. So on the picture taken with cropped sensor the depth of field is greater and amount of light getting to the sensor less than on a FF ,that’s precisely the same effect as having a higher f stop.. He is not making this statement solely on depth of field as you said.

    That’s the issue with focal length, aperture and ISO ,what they represent is usually dependent of a second factor, the angle of view depends on focal length of the lens and the sensor size, the depth of field depends on distance of the subject and aperture. Also in this context aperture fails to be a good measure of “lens speed” , a 1.4 lens on a MFT is half as fast as it would be on a full frame if you want to keep the same background isolation. FOV , DOF and total light gathered are the relevant factors since we have a variable sensor size.

    • J Shin

      He does sound like he is claiming that the manufacturers are claiming that sensor size “magically” changes the physical focal length of the lens. That is not right, either. He does not actually mention DOF in his discussion of the Panasonic example.

  • Ale, MR Admin

    Canon guys can make a simple test: Use the Canon 50mm f/1.8 lens on a Full Frame camera. Take a shot in automatic. Let’s say for example the shot is 100 ISO, f/1.8 and 1/250 shutter speed. Now use the same lens on a Canon APS-C camera. You wills ee the camera shot’s the same image with the same settings. The lens aperture doens’t change. It’s ALWAYS fixed when switching it from on sensors size to another.

    Where Tony is right is when he says that actual total amount of photons that hits a FF sensor is much larger on a FF sensor. But that’s why at same ISO the FF camera is less noisier.

    • Hubertus Bigend

      Tony nowhwere claims an existing lens would change its aperture when used with a differently sized sensor.

      But if you put a 50/1.8 FF lens on an APS-C camera, you don’t get the same pictures as the ones you do with a 50/1,8 on a FF camera. You’ll get pictures which will very much look like those you’d get if you’d used a 80/2.8 lens on a FF camera.

      And if a manufacturer would make a 50/1.8 specifically for APS-C that’s what he should add, if he comes out and claims this 50mm lens was the equivalent of an 80mm FF lens. Which it is, but it is the equivalent of an 80/2.8, not 80/1.8.

      Because if you take a real 80mm lens on your 5DII, set it to f/2.8, adjust ISO accordingly (add 2/3 EV), thereby getting the same shutter speed as with the 50/1.8 on that 7D, that’s when both resulting images will look as much the same as they will get between both cameras (give or take one or the other 1/3 EV stop difference in image noise because of possible differences in sensor efficiency, but that’s really about it).

  • Dmitry Anisimov

    >Just to say that the aperture remains CONSTANT and is not relative!

    BREAKING NEWS! f/# is relative by definition: it’s the entrace pupil diameter divided by the focal length. That’s why astronomers classify telescopes by their _absolute_ aperture, not f-stop.
    Even if Tony’s video has errors, this doesn’t mean the rumors admin is right.

    “ISO” is just a silly number relic from film era which only confuses people.

  • David Wei

    I guess if all he is concerned about using the lens to focus light onto a solar cell, or burn some ants, then he might be right.

    I guess this is why we all hate half-assed-self-appointed-know-it-all… :P

  • Mike stern

    Ale (admin), here are the corrections I can make.

    Tony is right about the facts. He doesn’t say, manufacturers should label their lenses differently. He says if manufacturers make comparisons to the full frame equals, then they should also mention the f stop facts. Which is correct.

    I am surprised to know Ale doesn’t agree with these facts. They are all correct.

    Tony, what the problem you caused here was, I wished you kept your article as it was with true calculations. And educate newbies about making logical purchases. The moment you brought in “cheat” good companies bad companies, you only lost the maturity of your article. Even though those were the words attracted me to watch your video. Your article will make a good call yet it will also attract haters to write to you in comments. Hope you are prepared.

    You are right about the misleading info manufacturers put out. But let others decide who is cheating, who is good who is bad.

    Admin’s advice about Tony should remove the video is not appropriate. The video is educational with proper facts, while not so proper on accusing manufacturers. It will speak to many people.
    M

  • Manus

    As far as everyone knows, f/# is the entrance pupil diameter divided by the focal length.

    Tony made a very low-level mistake: while he is multiplying the 35mm equivalent focal length on his calculation, he completely ignore the pupil diameter that also need to be multiplied. Everything goes wrong after that wrong assumption.

    After all, no one will bother to measure light volume by f/#, we use T instead

    • Hubertus Bigend

      Why should he multiply the entrance pupil?

  • Jacques_F

    Mr Tony Northrup: you call your video “TUTORIAL” but it is not only educational, it is also controversal only against some companies, and that is not fair at all.
    That’s mostly what people are reproaching to you, and you don’t want to recognize.

    SEE YOUR REPLY to one of my comment:
    “”For the record, after viewers found examples of Canon, Nikon, and Fuji doing the same trickery, I extended it to those companies… though the examples I cite in the video are still far worse.””
    “”Note that I did amend the video and the title to include Nikon, Canon, and Fuji in the cheating…. but they’re not nearly as awful as the examples I cite in the video. “”

    You should have presented your video without accusing some companies as bad boys and other as good boys. All companies including Canon, Nikon are doing the same (PLEASE look at the Canon web site link below).
    THAT’s IT and if you don’t want to recognize it, you are unfair !

    See Canon G1X MKII specs: http://www.usa.canon.com/cusa/consumer/products/cameras/digital_cameras/powershot_g1_x_mark_ii#Specifications

  • dirk

    Wow. How can you make things so complicated and confusing when you try to explain them?

    There are lenses and there are sensors/film. And both have nothing to do with each other. NOTHING!

    What does ISO have to do with sensor size? NOTHING!

    Let me explain this in three sentences:
    Take a full frame sensor, cut it in half and put it back in the camera. Here you have your APSC-camera, same noise, same ISO, same bokeh, same DOF. But only half of the image and thus, half the Megapixels and 1.5x field of view. End of story.

    Additon: Cut the sensor in quarters to get your MFT-camera. ;)

  • Mike

    These equivalence vs. light gathering discussions are pointless.

    They are flawed because people cherry-pick the equivalences they want to use to promote their product or brand.

    EITHER you calculate equivalence for one aspect (field of view, depth of field, light gathering) and *specify*. For example, a 12-35mm lens on micro four thirds has the same *field of view* as a 24-70mm lens on full frame.

    OR you pull the equivalence all the way through, e.g. 25mm f/1.4 ISO 200 on MFT === 50mm f/2.8 ISO 800 on FF.

    BUT NOT somewhere in between. You need to calculate the equivalence of the *full triangle* -> focal length, aperture, ISO.

    What happens with such full equivalence is that small sensor formats lose their “fast lenses” advantage, and large sensor cameras lose their ISO advantage.

    That’s why small sensor advocates cherry pick to promote “light gathering” of their pseudo-fast glass, while full frame advocates cherry pick to promote the stellar ISO performance of full frame cameras.

    Within the ranges of your lenses, there is no such advantage.

    The only real advantage of larger sensors is MORE CONTROL. Control over depth of field: you can choose an aperture down to f/0.95 on full frame while you could never get f/0.48 on micro four thirds. Control over light gathering: you can have a base ISO of 100 on full frame, while you could never dial in the equivalent ISO of 25 on micro four thirds. Control over resolution: if you choose the right lens and the right aperture, full frame can have 4x the resolution of micro four thirds. Control over dynamic range: full frame has 2-3 stops of dynamic range over micro four thirds.

    Of course not everyone needs such level of control, and for those who don’t, the smaller sensor cameras are a great alternative with their own advantages…

    • EcoR1

      Very well said. Just one additional point. For bigger sensors manufactures could always produce lenses with smaller image circle if some people would like to use smaller lenses with such a camera. Other way around is not possible. For this reason and all the other reasons Mike points out, bigger sensors will ALWAYS have more control and flexibility.

      • Dmitry Anisimov

        Lenses that don’t cover all image circle are wishful thinking, one could say that smaller formats have theoretical advantage too that you can have replaceable sensors for smaller cost (e.g. install B&W sensor instead of bayer), but neither possibility exists on the market.
        anyways, if we are talking about CaNikon FF, mirror in DSLRs does make using smaller image ineffective (lenses will be more retrofocus so prevents in gaining size advantage)

  • Benny Wong

    What about 120 medium format or even larger 4×5 8×10 format? Their DOF are much shallower than 135format. When is 135 become the standard to rule all lens aperture?

    • Hubertus Bigend

      It isn’t, it doesn’t and noone says it was or did. It’s just that all camera manufacturers like to use 135 format as a reference when explaining their smaller-sensor systems’ focal lengths. But they keep forgetting to explain that the reference lens would need to have a different aperture, too. The equivalence rule itself is completely agnostic to the sensor formats you want to compare.

  • Benny Wong

    The canon G1X2 should be a 24-105 F8-F16 aperture camera, right ?

    • Hubertus Bigend

      The equivalent full-frame lens for the G1X MkII lens would be 24-120mm f/3.8-7.5, as the compact camera’s sensor size is 1.5″, resulting in a crop factor of 1.92.

  • tekhiun

    I have to say that your critique to tony’s video is mostly wrong. Ale’s mistake seems to be that he thinks tony is saing that the physical aspect of the lens change. That is not what he is saying, it is all about the resulting image you get once you match composition.

    “No one cheats. All company aperture lens info are correct! The Panasonic 12-35mm f/2.8 has a f/2.8 aperture and not a f/5.6 aperture. You don’t have to make the equivalence he says has to be done! Use the Sony A7r and Sony A6000 for the same shot. To get same result the camera automatically sets on both the same ISO and same lens aperture despite the different sensor size. Just to say that the aperture remains CONSTANT and is not relative! There is no equivalence to make on that! ”

    That is a false comparison, you are disregarding composition. Tony is not talking about the physical aspects of the lens but the resulting image features once you start to match composition on different sensors.
    If you put the same lens on cameras with different sensors and shoot both on auto, they will get the same numbers , that’s because exactly what tony is saying, they will expose for total brightness and NOT expose for total light gathered, which is what Tony is talking about here.

    The physical aspects of the lens remain the same always,and he never claimed otherwise. However you don’t get the same image , manufactures know this and even if you look at the EXIF of a picture you will most likely find the 35mm equivalent focal length that’s because on different sized sensors the angle of view changes, just a the total amount of light gathered changes , which is why the other equivalent factors should be advertised as well not only focal length. A 2.8 lens on a MFT sensor will be as flexible as a 5.6 lens on full frame.

    “Second: He says Olympus, Panasonic and Sony do cheat. Nope. All companies use the same kind of measuring aperture for all lens formats (medium format, MFT format, APS-C and so on).”

    That is something that all manufactures do to some extent and that is a correct critique , and Tony addressed this already

    “After re-watching the video I am sure Tony confused “Focal length” with “Field of view” ! It’s the field of view where you can make the equivalence and not the focal length”

    He clearly states that he is changing the focal length because of the change in field of view. Again he is not saying that the lens has somehow changed but the image that you get does change. When you shoot with a lens at 2.8 on a MFT the total amount of light gathered by the sensor is less and the depth of field is also longer , if you match composition. That is equivalent to shooting with a 5.6 lens on a full frame. Just like the equivalent angle of view of a 80mm on a MFT is the one you get by using a 40mm lens on a full frame. The equivalence does changes according to sensor size.

    You are pretty much criticizing Tony on something that he is not claiming.

    Imo the system we use nowadays is misleading and antiquate , I wouldn’t say that companies are always cheating when they don’t do all the equivalence changes. However when you market a lens made specifically to a cropped sensor and you make it seem like the aperture will give you the same benefits that you would get of using a lens of that focal length and lens speed on a full frame camera that is clearly misleading customers and that is the whole point Tony is making.

  • Andrea P.

    I really like Tony and often go to his very well produced videos to educate myself on photography. In this case, though, I think the complexity of the issues involved clouded the argument quite a bit. He certainly seems to be suggesting that a 2.8 lens on a crop sensor is not a 2.8 lens. True, if you want the same field of view, the same background blur, and the same sensor noise performance in two shots of the same subject, the only way to get it is to use the same sensor with the same lens.

    If you want two comparable portrait shots of the same subject with the same background blur, taken one with a crop camera, one with a full frame, then something has to change. If you change focal length to account for the crop but keep the same aperture and the same distance to subject, you will get almost the same framing and almost the same background blur. Say, 50mm 1.8 and 35mm 1.8. The crop sensor image will be noisier, sensor technology being equal.

    If you take a full frame sensor (D800 or D600) and mask the outer area to simulate a DX crop, the noise performance will be exactly the same regardless of lens or aperture used. Of course, you will have diminished the image size (Megapixels). If you match image size between DX and FX, then you will have to use smaller sensels (is that the right word?) and you will increase noise (provided the technology is the same). A more advanced DX sensor may cancel that difference, but the same more advance technology on FX will make FX even cleaner.

    So I think Tony’s argument is valid only if you want the same noise, the same angle of view, and the same level of background blur. In other words, what he says has more relevance for portraits than it does for landscape shooting where you want everything in focus.

    Also, many gathered from the video that aperture should be multiplied by the crop factor. This is only relevant to background blur at the same distance to subject, on equivalent angle of view. But the amount of light coming through a 2.8 lens will be the same, or should be the same for all 2.8 lenses, regardless of format. Otherwise hand-held light meters would be completely useless (as would be the Sunny f/16 rule). F-stop is a ratio between entrance pupil size and ACTUAL focal length. If you multiply it by the crop factor, you are calculating f-stop against PERCEIVED focal length, which is only useful if you want to keep the same angle of view, background blur, and sensor noise performance.

    True: a 12-35 2.8 will never give you the same background blur as a 24-70 2.8 at 2.8, but 12mm 2.8 on MFT will give you the same background blur as 24MM 5.6 on full frame, right? So there is no way to meet exact equivalence at the open end. But if you are willing to accept a little more sensor noise, to change focal length and distance to subject, you can achieve very similar effects.

    Where it all breaks down for me is Tony’s points on bridge cameras. Those 2.8 lenses at 200mm would get the same shutter speed at the same ISO as a full frame lens with the same specifications. Of course, the resulting image would be noisier on the one inch sensor, but if are willing to accept the noise, because you do not print and view images on 1MP screen without pixel peeping, you get comparable results. As soon as you “zoom in” then things break apart for the smaller sensor.

    If you are so obsessed at keeping noise performance constant, then full frame cameras are not equivalent to full frame cameras. With the same settings, an image from a D700 will have different noise levels than the same image with the same lens on a D800 or a D4. Should there be an ISO crop factor for that also?

    Just my two cents. Feel free to correct errors in my logic or equivalence estimations. I am here to learn, after all.

    • Hubertus Bigend

      “He certainly seems to be suggesting that a 2.8 lens on a crop sensor is not a 2.8 lens” – no, he isn’t. Not at all.

  • Jeff Smith

    F-stop is the focal length of a lens divided by the maximum diameter of the lens opening (aperture opening). It is a simply mathematic calculation. There is nothing to cheat on providing the measurement of focal length and maximum lens opening are accurate. So I don’t think anyone is cheating.

    However, what a given f-stop looks like does vary dramatically depending upon sensor size, with a given f-stop having a shallower depth if field on a larger sensor compared to the same f-stop on a smaller sensor camera. But in both instances the f-stop value is the same as it simply focal length divided by lens opening.

    So no cheating on the numbers but a different look.

    • tekhiun

      And so is focal length and yet it gets the equivalent conversion when what actually changes is the maximum field of view.
      I think this whole discussion underlines how inappropriate these terms are when we make the sensor size a variable. Imagine now that the sensor size remained the same but what actually changes is the flange distance. Well you don’t even have to imagine we can change that by using a teleconverter, the same issues arise then , regarding the image quality.

      • dirk

        Flange distance has nothing to do with anything discussed here. Let’s not make it even more confusing.

        • tekhiun

          It does have a similar effect to changing the sensor size on the final image with the same composition. The only confusion here is that some people think that the crop factor conversion means that the property of the lens change. I don’t think anyone is claiming that, what changes is the quality of the image in regards to FOV, DOF and total light gathered.

          • dirk

            No. Changing the flange distance has no effect whatsoever. I think you confuse it with focal length. Flange distance is a matter of camera and lens design.
            A 50mm on an M Rangefinder will give you the same image as a 50mm on a SLR with a much longer flange distance except for the different character of the lens of course.

          • tekhiun

            Changing the flange will change the focal length by definition. The focal length is basically the distance from the sensor to where all light entering the lens converges into a single point and starts diverging into a projection. The reason these lenses will have the same focal length with different flange distances is that they are manufactured specially for that type of mount. If you put the lens from the range finder on the slr you will get a different image.

          • Hubertus Bigend

            If you put a rangefinder lens on an SLR, you won’t get a (sharp) image at all except for objects at a close distance, because that’s just as if you would have used an extension tube. Technically, you’ve changed the focal length, too, but that’s not the point when changing the distance between sensor and lens, which is the classic way of focusing.

          • dirk

            Focal length does not change when you change the flange distance. It is a fixed optical property of the lens.

          • Hubertus Bigend

            No one seems to know it these days, but it really is one of the most basic rules of optics. To increase the distance between the lens and the focal plane means increasing focal length. That you don’t get sharp images of distant objects anymore if you do increase that distance is a different matter altogether.

            A classic lens with a conventional threaded focusing mechanism simply extrudes its inner barrel until the closest object distance is reached. Doing that, focal length increases, too.

            It’s most obvious in a classic macro lens. Try this: If you attach it and look into your viewfinder, optimally while the aperture is stopped down as far as possible, set it to infinity and watch the angle of view change while focusing closer and closer. You’ll see how the angle of view gets smaller and smaller, while the focal length increases.

            Increasing the flange distance is physically the same as using an extension tube, so it does increase focal length just in the same way. It removes the ability to focus to infinity in just the same way, too, of course, with a lens that has been designed for the shorter flange distance.

            (edited: field of view -> angle of view)

          • dirk

            Sorry, but you are not correct. Changing the distance between lens and sensor/film is called focusing. This is done because the image plane for a lens is at the focal plane only for focus set to infinity.

            If you focus your lens closer than infinity your IMAGE PLANE is no longer identical to your FOCAL PLANE. Focal length will be the same however. This does change the field of view slightly, which is not equivalent to changing the focal length.

            In Macro photography your image plane is usually very far away from the focal plane, about one focal length for 1:1. The image plane is now twice the focal length away from the rear principal plane. This does change the field of view significantly. Someone might also call this distance the effective focal length, which is a bit misleading.

          • Hubertus Bigend

            Not at all. It is what focal length is and always was defined to mean, and there’s no need to use the word ‘effective’.

            Actually, technically and physically, there is no such thing as a fixed focal length. The nominal focal length is by convention defined as the focal length at infinite distance, but it in fact increases as distance decreases, as long as no internal focusing mechanism is used which changes the optical formula while focusing.

            By the way, I have erroneously used ‘field of view’ instead of ‘angle of view’ in my last post. I’ll edit that.

          • dirk

            The focal length of an optical system is a physical constant. It is easily measured and defined as the distance at which light parallel to the optical axis is focused into one point.
            This is technically physically actually really constant. For one medium, lets say air at normal pressure that is. You can call it a convention but it is a law.

            It does not matter what you do or put in front or behind the lens. It is fixed. Unless – as you said – you change to optical formula with some floating elements. Then it might not be constant.

            No one seems to know this these days.

          • Hubertus Bigend

            Sorry, but no, it is no law, it is an error. The focal length of a lens is specified for infinity, and it is considered fixed only for practical purposes, and because, in a conventional, non-internal-focus design and within non-macro focusing distances, it does not change extremely.

            Here’s the formula: http://hv.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=008MQJ

            From there: “Many older Leica lenses have a numeral on the focussing ring next the the feet/m engraving which indicates the [focal length; HB] deviation from nominal at infinity.”

          • dirk

            So what you are saying is that the focal length does not depend on the lens but on the distance from lens to image plane?
            And you have a 12 year old board entry on a family server to back that up?

          • Hubertus Bigend

            No, that’s not at all what I’m saying.

            But if you believe the underlying knowledge from the optical sciences must be younger than 12 years, which you have to if you find a 12 year old link to an optical formula objectionable because of its age, you are excused for thinking that, too.

            The link says, although in less than perfect English, “when d= 2f, d=D, the image size = object size”.

            The best thing is, everyone can check that for themselves with an old macro lens, as I already described. If you focus as close as to get to 1.0x magnification, the focal length will have exactly doubled, and the angle of view become exactly half of what it is for infinity.

          • dirk

            The problem is not that it is 12 years old, but that is a family server. Come on!
            By the way, the entry you cited the formula from also says: “the focal length of lens(except varifocal lens ) is regarded as a constance”
            This is from a different user who contradicted the former entry you mentioned.

            d=2f where d is the distance of image to rear principal plane. f is the focal length and remains constant. That is exactly the difference I tried to explain to you all the time.

            However, if somebody is interested in the matter I recommend wikipedia. Not some random site that seems to support your opinion on first sight.
            You can start here:
            http://en.wikipedia.org/wiki/Focal_length

          • Hubertus Bigend

            No need for re-education through Wikipedia here, I was taught about the matter in question just recently by a photog whose training includes having studied physics at uni with optics as a major field.

            Just tell us: how come that a 50mm macro lens, when focused as close as to get to 1.0x magnification, shows exactly half the angle of view compared to what we get at infinity, if not by increased focal length. Given that the image area stays the same, how can the angle of view change without changing focal length?

          • dirk

            Space is really getting thin down here. The reason is that focal length and field of view are only directly correlated in the pinhole model. That is a good approximation for long object distances but does not hold any more if you go into macro photography.
            You need the physics of real optics then.

            Maybe you can ask that photog again to give you the whole story.
            By the way, did he just study physics or did he get a degree?
            I am trying to give you facts. Not things some “expert” told me.

          • Hubertus Bigend

            Embarassingly, I have to backpedal indeed. Seems I’ve been confusing focal length and image width. Looks like what I was claiming would be true, if at all, only for what you correctly called “effective focal length”. Thanks for the patience!

          • dirk

            Been there, done that, don’t worry. ;)

          • dirk

            As I said, you mistake flange distance with focal length. What we call focal length of a photographic lens is the effective focal length, which is the distance of the rear principal plane to the rear focal point. That is the same for any 50mm lens. No matter the flange distance, sensor size or whatsoever.
            As you said, lenses have different flange distances because of different systems. It does not change the field of view!
            If you put your rangefinder lens on a slr you will get a different image because all you get is blur. If you are lucky you can do some really really close macro shots but this is a different story.

          • Andrea P.

            I agree up to “total light gathered”; I don’t think that is a useful measurement. If you take a crop sensor and you make it as large as a full frame sensor (but keep the same pixel density, so you don’t enlarge the photosites) you end up with a full frame sensor with 1.5X the megapixels of the crop sensor, but with exactly the same characteristics in terms of noise. The total light gathered will be the same as the larger sensor, and so will the DOF and FOV, but noise will be different, so you will not have the same picture. Sensor noise depends on the size of photosites, not the size of the sensor. Amount of light per fotosite stays the same with lenses that have the same aperture. If they photosites are bigger, they collect more light and produce less noise, if they are smaller, they collect less light and produce more noise. Tony’s claim that he is not talking about pixel level is a bit disingenuous.

          • tekhiun

            That is true, but at the same time i would think that this is not a realistic example, as in most companies wouldn’t just keep the same pixel density when scaling up a sensor. Pixel level noise is quite complex on its own it’s not only about pixel density but also on the technology in general regarding the sensor such as which demosaicing algorithm is being used.
            Also as he mentions image level noise is more important than per pixel noise when evaluating images qualitatively.

            Total light gathered is important but if you want to take into consideration per pixel noise then we should also add signal to noise ratio to that metric.

        • Mk.82

          Flange distance change exposure value. Shorter distance between focal point and focal plane gives more light to sensor than longer distance. That is the fact.
          Flange distance changes angle of view and exposure.
          But throw there optics and electronics and there are new problems with angles and reflections and distance ratios between edge and middle of film/sensor.
          And there is reason for telecentric designs and curved sensors.

      • Andrea P.

        Not really. ACTUAL focal length remains the same. What changes due to the crop sensor is PERCEIVED focal length. The amount of light that can get through the wide open iris remains constant; you multiply pupil diameter by actual focal length. The lens is not at fault if a smaller sensor with greater density produces more noise than a larger sensor with larger photosites, at the same megapixel count.

        I am not sure I follow what you mean by changing flange distance, unless you’re thinking of what Sony did with the A7/A7r: same sensor size as D600/D800, shorter flange distance. The use of well made adapters with no glass elements has no impact on image quality.

        • tekhiun

          ” ACTUAL focal length remains the same. What changes due to the crop sensor is PERCEIVED focal length.” I know that’s what I meant with “equivalent conversion” what actually changes is the FOV.

          All i meant with the flange distance is that if somehow we had a system where that was the variable factor , focal length and aperture would also become loose terms because they would vary from system to system. In this hypothetical they would actually change, however the perceived image would not ( I think , haven’t done the math on that).

  • OnLocationAfrica

    That´s definitely wrong since the f-stop number only qualifies the amount of light getting to the sensor through the lens. It´s no qualification for bokeh or anything else. Actually it´s more or less right, so if you really want exact amount of light you use T-stop (dxomark is measuring that). Iso on Full Frame, Apsc or MFT is always the same since an Apsc lens is calculated for an Apsc Sensor and using all the light coming through the lens, while a Full Frame lens on Apsc sensor is waisting the light around the sensor. That´s also the way metabones is catching that wasted light and using the Apsc sensor size only which gives you around one more f-stop (inclusive less dof – nicer bokeh) from a Full Frame lens on Apsc sensor. So shooting at aperture 1.4 and Iso 6400 is the same shutter time on any sensor format and that´s what the f-stop number is made for – calculating your shutter time or and Iso. Bokeh etc. is of course smaller or usually less when using a smaller sensor at same focal length (crop equivalent). Also noise is always less on a full frame sensor (same generation cameras). I think the manufacturers are doing right like they do it – you know your crop factor anyway and so lenses are compareable.

  • Roco A. Del Rosario

    It’s great to come across your site. Tony northrup is doing a disservice to photography by releasing this video. He’s spreading wrong information. I commented a lot in his youtube video and maybe that is why the title of his video was changed. I hope that he’ll soon take down that video and apologize for the errors he made.

  • Keiki

    I think the biggest mistake tony northrups make is only “dslr” maker such as canon and nikon or another is the only good guy.
    is he have some plot to cripple mirrorles reputation?

    • Hubertus Bigend

      Yes, that was his – one – mistake. But he admitted and corrected it. And if you saw the video, you will know that he happily uses mirrorless cameras with smaller-than-FF sensors himself and values them highly. So, again, what?

  • David Cuellar

    After reading through everything, I have to say that I’m in shock that the admin Ale doesn’t understand. This website just lost a lot of credibility for me.
    The idea of equivalence is a simple one, and reading Ale’s argument makes it clear that he doesn’t get it. He’s worried about exposure and how it is affected, and he refuses to listen to the other properties involved with aperture, focal length, and sensor size and how they affect an image outside of exposure. To prove his argument isn’t correct , I challenge him to make the SAME EXACT image with the same EXPOSURE AND DEPTH-OF-FIELD like Tony did in his video multiple times, but do it with f/2.8 on a crop-sensored and f/2.8 with a full-frame or medium-format camera. Impossible without cropping.

    That’s not to say that Tony isn’t at fault to some extent, however. Firing shots at camera manufacturers the way he did wasn’t correct, but at least he acknowledged he was wrong. He is factually correct and has fixed any mistakes, so if you just watch the damn video the whole way, you will get his argument and see that he is correct on the physics, math, etc. involved.
    But the problem is that people buy their gear thinking about exposure most of the time (apparently Ale comes from this point-of-view), so it’s not so bad to say a 25mm f/2.8 M43 lens’ field-of-view is equivalent to a 50mm full-frame (and therefore for a different sensor size) AND provides the same “brightness” of a f/2.8 lens. BUT they aren’t allowed to say the f/2.8 will provide the same amount of depth-of-field simply because that is a property that is affected by SENSOR AND APERTURE, and we already distinguished that the sensor sizes are different.
    To reiterate: Exposure/brightness and depth-of-field are on two different continuums, two different properties that aren’t always equal when camera manufacturers advertise the way the do.

    That is all.

    • Hubertus Bigend

      Right, and equivalence actually is more than just DoF – it’s about the requirements under which two setups with different sensor sizes will tend to offer the most similar options and to deliver the most similar images, of course including DoF, but including sensor-based image quality, too.

      I more and more find that people on the Net opposing the rule of equivalence come across not even like creationists but more like those people back in the 16th and 17th century who kept opposing physical and astronomical truths like the simple fact that earth revolves around the sun and not vice versa.

      I’m sorry for this site, too, that its editor chimed in with the deniers, which indeed made it lose credibility and seriousness.

    • Andrea P.

      Depth of field is affected by focal length, aperture, and distance to subject. Sensor size has nothing to do with it. It seems to because, to get the same framing on a crop sensor, you have to change distance to subject. So, with the same 50mm lens on FX and DX, you will have to step back on DX to achieve the same framing, and that will give you a different DOF effect. If you change the focal length of the lens and use 35mm on DX with the same aperture as the FX lens, say 50mm at 1.8 vs 35mm at 1.8, you get the same picture. There will be a difference in noise, but that also has nothing to do with sensor size. It is determined by the efficiency of the photosites that will be smaller on a higher density sensor.

      • David Cuellar

        Thanks for clearing that up, I guess that’s one detail I still have to do a little more research on since I’ve always thought of it as the sensor’s size at the same position, rather than the distance from subject to sensor plane.

      • MikePukmel

        Oh yeah! Thanks Andrea. That’s what I arrived at, after picking through my old physics, what little I could remember. If we took two cameras, one FF and one M4/3, from similar generation, similar quality manufacturers, (i.e. not one 10 years old and one new), got two similar spec lenses, e.g. 70-200, and set the same numerical values on both cameras, e.g. 100mm @ F/2.8, and took the shots. Then, cut the center portion if the FF image out that corresponds to what image would have been captured by a M4/3, then, the images should look very similar. After picking at literally thousands of images on Flickr and similar sites, that seems to be the case.

  • Albert

    I think Tony Northrup is RIGHT and that Crop factor is applied to PRICES!

    Take for example the Olympus 75 mm f/1.8 it costs twice (or more) than an 85 mm f/1.8 from Canon/Nikon.

    WHY?

    Because Olympus is taking in consideration Crop factor, so they are selling is as 150 mm (equivalent) lens. NO, this is a 75 mm and should be priced for what it is!

    They are CHEATING, like Tony says!

    Field of view equivalence does not increase production costs. MFT lenses even uses less glass (smaller sensor = smaller lens = less glass) so less raw materials needed.

    So WHY the 75 mm is so expensive?

    Roger Cicala of LensRentals told us that is well built (http://www.lensrentals.com/blog/2012/07/the-olympus-75mm-f1-8-is-expensive-because-its-worth-it).
    Ok but I think he was misled by Crop factor too. In fact he compared the 75 mm to Canon 135 L, Nikon 135 DC, Sony 135 f/1.8.
    Roger, you are an experienced guy, this is not physically a 135 mm (or 150mm), this is a 75 mm and should be priced for what it is. It is well built, ok let’s price it 100$ more than other than 85 mm lenses available from Canon/Nikon etc.

    Am I WRONG?

    • Hubertus Bigend

      No, you aren’t…

      I think the prices manufacturers demand for mirrorless lenses have two reasons.

      For one, although it doesn’t need to achieve it for the same image circle, a Micro Four Thirds 75/1.8 lens must offer twice the optical resolution (lp/mm) of a full-frame 85mm f/1.8 lens, if both want to satisfy the demands of similar megapixel counts (or lp/imageheight; I know today FF offers 36 MP and MFT only 16, but MFT will probably increase that before FF will increase it further, and MFT lens designs must account for that). Therefore the MFT 75/1.8 has to be a significantly “better” lens with regard to what would be center image quality for a FF lens than that FF 85/1.8 lens.

      The other reason, of course, is that manufacturers can afford to ask the prices people are ready to pay, and, although I don’t know why, people still seem to be ready to pay much more for most of the mirrorless gear (except for some of the most basic entry-level stuff) than for comparable DSLR gear. Of course, some people being misled into thinking a 75/1.8 MFT lens was equivalent to a 150/1.8 FF lens does help here.

      • dirk

        I guess you are right with the optical quality.

        Also Canikon sell ten times or more the amount of lenses and have done most of the development spread over the last decades. Mirrorless companies have to do this now in a very short time and need to get the money for that back from a lot less units sold.
        It’s not like the Mirrorless companies get filthy rich with their prices. They even make a loss. I wouldn’t call that cheating.

        • Hubertus Bigend

          I agree that some of them still fail to make profit, so from an operational business point of view, and because the number of pieces they manufacture is indeed still far below Canon’s and Nikon’s mass production figures, those prices could indeed be considered reasonable. Trying to increase sales by making people believe an MFT 75/1.8 lens would offer the same options and produce the same images as a FF 150/1.8 lens, though, is still cheating.

      • Albert

        I agree with you. But, in my opinion, the first reason does not justify the huge price difference between FF 85 mm f/1.8 and MFT 75 mm f/1.8.
        I think the second reason is what drive the choice of the final market price.
        In this regard I remember the Canon EOS M huge price drop http://www.cinema5d.com/news/?p=19980 we need the same price drop for the 75 mm f/1.8!

  • Tim Bull

    Well so much for clearing anything up. I was having a pretty good day till I stumbled on this mess of confusion So thanx everyone. Thanks a lot.

    • Andrea P.

      Ha ha ha!

      • Tim Bull

        Hilarious ain’t it.

    • dirk

      It is very simple once you get the right ideas. I’ve written this before:

      Take a full frame sensor, cut it in half and put it back in the camera. Here you have your APSC-camera, same noise, same ISO, same bokeh, same DOF. But only half of the image and thus, half the Megapixels and 1.5x field of view. End of story.

      Additon: Cut the sensor in quarters to get your MFT-camera. ;)

      Equivalence is only given so you have an idea what field the of view is. And as long as they call it “equivalence” and not actual focal length you only cheat yourself if you don’t know what it is all about and assume things you don’t know.
      The video only makes things more confusing by messing everything up. Culminating in writing SNR = P/sqrt(P). If you want to make it simple you could just write SNR = sqrt(P). But that is not the whole story. It only refers to photon shot noise. There is so much more that influences the noise and low-light capability of a sensor.
      I hope Tony Northrup has a good lawyer. Accusing somebody of cheating when he is not can be quite expensive.

      • Hubertus Bigend

        “Take a full frame sensor, cut it in half and put it back in the camera. Here you have your APSC-camera, same noise, same ISO, same bokeh, same DOF.”

        Only if you don’t care for real-world images, which don’t suddenly start varying in output size just because someone shoots with a different sensor size. For a fixed output size things already stop being the “same” where you say “noise”.

        “Equivalence is only given so you have an idea what field the of view is.”

        If that was what manufacturers were taking care to convey, nobody would complain. Fact is, they often explicity state the physical aperture alongside the equivalent focal length. And noone needs a lawyer for being more than entitled to call that cheating.

        • dirk

          Testing my patience again?

          Please elaborate what exactly changes if you switch to “real world” images because noise is definitely not one of them. Of course you have not the same resolution for prints because we just cut our sensor in half. I mentioned that.
          But back to noise: I know in the video there is some talk about “per image” noise, different to per pixel noise. I’m having a hard time to bend my head around what “per image” noise is supposed to be and how it is different from per pixel noise. Noise is a result of statistical processes and the statistics does not change if you have one pixel or 1 billion.

          About how well or not manufacturers inform customers about equivalent focal length and focal length and the respective effect on aperture everybody is entitled to his own opinion. From a photographic point of view the real aperture is far more important than the aperture equivalence with respect to depth of field because the real aperture allows you to calculate the correct exposure. If you want to know about depth of field you can just use the real focal length. And really, how many different numbers do you want to throw at consumers?

          • Hubertus Bigend

            The same level of noise is the more detrimental to image quality the less pixels there are. Much of what DxO does is faulty, but in http://www.dxomark.com/Reviews/More-pixels-offset-noise they’re right, and that’s the principle behind the need to differentiate between per-image and per-pixel noise.

            Your “photographic point of view” means that you (1) refuse to adjust ISO to suit your needs and (2) care more about shutter speed than the visual properties of your image.

            And how many numbers? The same amount or one less, if what the manufacturer does is boast the original aperture together with the equivalent focal length. If they give us numbers, they need to give us the correct ones.

          • dirk

            Great example. As I said: “Of course you have not the same resolution for prints because we just cut our sensor in half.”
            We cut our Sensor in half, so we also have to cut our print in half to keep the same relative resolution. What makes the noise in the full frame picture appear to be less is that you sample it down! So you do have less noise in the picture but also less resolution. You can not expect to cut away half of your sensor and expect to get the same picture. You only get, as I said: “same noise, same ISO, same bokeh, same DOF”. Not the same picture, but only half of it. You can always sacrifice resolution for less noise.

            ISO a a sensor/film property. It is and always was independent of the sensor/film size and especially independent of the lens! You can shoot in the same scene with the same ISO and the same aperture with any lens and any sensor/film size. If you give the “equivalent aperture” you can not do this. Do not mix up film/sensors and lenses only because they are usually used together. This will only make a mess.

          • Hubertus Bigend

            The problem is, your sensor-cutting story is, on one hand, trivial, and on the other hand worthless, because no one who switches from one camera to another with a smaller sensor will say oh, wow, smaller sensor, now I have to order smaller prints, too.

            And if you say, “you can not expect to cut away half of your sensor and expect to get the same picture”, you’re wrong again. You can, and you will – as long as the output size stays below the limits of the cut-down sensor resolution, if you only choose the right lens and the right settings. Which exactly is what equivalence is about.

            Demanding that people should artificially separate ISO from the lens’ settings is a supremely ideological call. In a digital camera, they are without each other what the lens is without the camera and vice versa. A photographer who cares about what his images will look like, instead of purely technical, theoretical and, really, ideological concepts about what and when you can shoot “with the same ISO and the same aperture”, chooses his ISO so that he can achieve the DoF he wants, that he can use the shutter speed he needs, and that image noise will not exceed beyond what he finds acceptable.

          • dirk

            Yep, it is trivial. That was my point in the first place. (Why are you trying so very hard to find mistakes in my posts?) Explaining the difference between full frame, aps-c and m43 ist trivial. You don’t need a 40 minute video where you question the concept of ISO and f-stops.
            About the sensor-cutting: I also said we put it back in the camera. That implies the same camera with the same lens. (Again, why are you trying so hard?)
            I don’t really get what you are trying to say about ISO and photographers there, but I don’t see why anybody should deviate from a proven international standard because some photog mixes up illuminance and luminous flux. Granted, it is not really well defined for digital sensors but that has nothing to do with the sensor size again.

          • Hubertus Bigend

            No one mixes up things here, except maybe you, since the amount of light that reaches a sensor is, of course, dependent on sensor size. The photographer does not even need to know those definitions, though, as long as he knows how the ISO settings of his specific cameras affect image quality and detail resolution. In the end it’s primarily geometry that is needed as a guidance for choosing the right gear for one’s needs when taking different sensor sizes into account. And although it surely wouldn’t need to take 40 minutes to explain (which was my own first complaint in this comments section, by the way), that’s what is being explained correctly in that video.

          • dirk

            Well, this argument doesn’t make sense anymore because we are constantly calling mistakes that only occur when changing the premise.
            So I will end it here.

      • Seamus of the North

        >>>Take a full frame sensor, cut it in half and put it back in the camera. Here you have your APSC-camera, same noise, same ISO, same bokeh, same DOF. But only half of the image and thus, half the Megapixels and 1.5x field of view. End of story.<<< Yeah, or use a full frame camera in cropped mode? As far as I am aware the lens remains as bright because "...the distance in mm from the optical center of the lens to the focal point... (sensor/film) does not change.

  • Seamus of the North

    At 22:20 Tony describes the formula for determining aperture where “F” (focal length) divided by “D” (lens iris) = “N”.

    Tony later gives the example of the LUMIX 12-35 f/2.8 and describes the formula for determining aperture – 35/12.5 = f/2.8 – is in fact erroneous because the 35mm camera equivalent focal length is not been taken into account.

    This appears to be where I start to lose the plot because I am under the impression the long end 35mm focal length of the Lumix 12-35 remains the same independent of the size of the sensor or light sensitive material to which it is attached as long as:

    “…the distance in mm from the optical center of the lens to the focal point, which is located on the sensor or film…” (in the case of the Lumix 12-35) remains 35mm and the lens iris remains 12.5mm.

    Thank you dpreview and Vincent Bockaert: http://www.dpreview.com/glossary/optical/focal-length

    I don’t understand how the focal length of the Lumix lens would double to 70mm.

    At around at around 21:55 in Tony’s video, where a table describes a “…35mm camera equivalent 24-70mm…” in relation to the Lumix 12-35 f/2.8, is merely describing a perceived equivalence in picture angle.

    Tony’s video is “doing my head in”. :)

    Am I losing my marbles? :)

  • Seamus of the North

    My understanding is lens brightness is calculated independent of sensor size.

    An M43 Lumix 12-35mm and FF Nikkor 24-70mm are both legitimate f/2.8 lenses.

    Imagine two sky lights of differing diameters each shedding a circle of light on a dark floor. Neither circle of light is brighter or dimmer than the other.

    Perceived depth of field can vary due to the so called “crop factor”, but not brightness.

    I found this useful: http://www.dpreview.com/glossary/optical/focal-length.

    Thank you. :)

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