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Crop Factor with ISO & Aperture: How Sony, Olympus, Panasonic, Canon, Nikon & Fuji Cheat You

Discussion in 'Back Room' started by Klorenzo, May 19, 2014.

  1. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    Hi,
    I have just seen this video and I think he is right.

    https://www.youtube.com/watch?v=DtDotqLx6nA

    If you are in a hurry, the part about aperture equivalence, IMO the most interesting, starts at 20:20.

    I'm not so convinced about the "marketing cheating" part: from one point of view they are giving a false information, but at the same time they are saying something most users can understand. It's quite borderline to me. Anyway I think it's a good thing to know to better understand why and how a 300mm 2.8 can be so small (it cannot) and so on.

    Just to be sure I got it right I took an adapted FF Nikon lens and an Oly native lens and I took the same shot with the same three exposure values and I got the same brightness in the two pictures. So, if the Nikon lens at 2.8 has twice the physical opening of the Oly at 2.8 where is the extra light gone? I suppose it just bounced against the adapter and on the area around the sensor and got reflected outside of the lens.
    But more light enters the lens and that's why I can use a speed booster to use that extra light. And this is also why I cannot use a speedbooster to boost a Oly lens from 2.8 to 1.4. Am I correct?
     
  2. taz98spin

    taz98spin Mu-43 Top Veteran

    843
    May 13, 2011
    NYC
    There's already a thread covering this topic and video.. you guys are just giving the youtube poster more clicks and traffice :mad:
     
  3. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    Yes, I found it a couple of minutes ago. As I said there I found the last part quite interesting and I am happy to give clicks and traffic.

    BTW, can you answer my question about the speed booster?
     
  4. taz98spin

    taz98spin Mu-43 Top Veteran

    843
    May 13, 2011
    NYC
    Sorry, I must have missed your question.. but what about the speed booster??
     
  5. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I think that he is right when he says that a 2.8 aperture on MFT is actually (physically) a 5.6 aperture. That is the reason why you can use a speedbooster to boost a FF 2.8 lens to more brightness and why you cannot do the same with with a native MFT 2.8 lens. It's a question, I mean, is this correct?
     
  6. Cruzan80

    Cruzan80 Mu-43 All-Pro

    Aug 23, 2012
    Denver, Co
    Sean Rastsmith
    No, that is wrong. Aperture is a mathematical formula about the size of the opening vs the focal length. It has ZERO to do with any sensor size. The physical size is what it is. A 25mm focal length lens with an aperture of 1.4 has a physical opening of 17.85mm. 25/17.85 is 1.4. The reason you can use a speedbooster on certain lenses is because the image projected is larger than the sensor. The extra light isnt recorded by the sensor, because it falls outside of it. The speedbooster condenses the image to a smaller circle. This makes a lens act like it is a wider focal length lens, while leaving the phyical opening the same. This means it acts like a faster aperture.

    Take any two lenses, from any format. If you put them at the same aperture and same ISO, they will read the same shutter speed for the same scene. The Oly 75 at f2 has almost double the physical opening as the Oly 45 at f2, but render the exposure the same. The Olympus 45 and my Minolta MD 45 will have the same pupil at the same aperture, even though one is designed for 35mm and one for m4/3. Sensors dont play into it.

    Sent from my LG-P769 using Mu-43 mobile app
     
  7. taz98spin

    taz98spin Mu-43 Top Veteran

    843
    May 13, 2011
    NYC
    In all honesty, I'm at work so started the video but closed it after reading the rediculous title and some of the comments in the video.

    As for the speed booster question, I don't know?
    But the way you worded it asking a "2.8 aperture on MFT is actually (physically) a 5.6 aperture", yes, it would be if you were trying to use the 2.8 apeture m43 lens on a FF camera sensor.

    But like many others have pointed out, a 2.8 lens built for m43, is a 2.8 lens for the m43 sensor.
     
  8. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    So... What's your point? f-stop is a measure of exposure. It is not now, nor has it ever been, a measure of physical size.

    Absolutely not, it has nothing to do with it. You can use a focal reducer on a MFT lens. It just has to be designed for the appropriate registration distance, and require a sensor mount that is has a sufficiently smaller registration distance to allow the adapter to fit between the lens and the body. Which means that obviously it won't work with a m4/3 lens on a m4/3 body, just as you can't use one on an F mount lens on a Nikon F mount body.
     
  9. lightmonkey

    lightmonkey Mu-43 Veteran

    480
    Dec 22, 2013
  10. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    He wasn't using the correct term to explain DOF. DOF has to do with sensor size and it is due to the difference in the circle of confusion. Full frame has a circle of confusion of 0.030mm, whereas m43 has a circle of confusion of 0.015mm.
     
  11. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I think we are saying the same thing. I never said aperture is related to sensor size.

    25 / 1.4 = 17.85
    50 / 1.4 = 35.71

    So I think the 50 mm "pupil" is bigger than the 25 "pupil" and this means that more light pass through, is this correct? So when I set the 50 to 1.4, on the same MFT body, I'm letting in more light (even if a lot of it does not reach the sensor).

    So when someone says that the 25 is equivalent to a 50 angle of view he's saying a correct thing. But he also should say that the "pupil" is smaller if compared to the pupil of a real 50mm. Is this correct? I mean, it's no big deal, I think it's quite obvious. Am I wrong?
    Of course the picture brightness does not change, but I'm not talking about exposure here.

    About the speedbooster see my first post: I think we are telling the same thing. So you cannot make a speedbooster for an MFT lens on a MFT body because there is not extra light spread around.

    I agree. But the Minolta 90mm at the same aperture will have a pupil twice the 45.
     
  12. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    The reason 2.8 aperture on MFT is twice as of that of a full frame equivalent is due to the circle of confusion. He's confusing aperture with DOF; where he should have said that the circle of confusion of a full frame is 0.030mm and the MFT has a CC of 0.015mm, which is -- guess what -- 2x. Photography is a 2 dimensional art; whereby ONLY ONE PLANE in the picture is technically sharp. The front and back of this one plane of focus are only sharp based on perception and is the result of the circle of confusion. Exposure is based on Ev (Exposure Value) and based on a combination of f-stop (Av) and Tv (Time value = shutter speed), not f-stop.
     
  13. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I think you are talking about exposure here and you are correct, of course. But I'm not talking about exposure.

    The only thing that the video says it that if you choose to multiply the focal length of a lens to compare it to a FF lens you should also "recalculate" the aperture.
    Not in terms of exposure, that does not change, but in terms of simple calculation of the aperture.
    Is it useless? Is it silly? Maybe, but I think he's not wrong. He says: if this lens would be a 300mm the aperture would be 13 or whatever.
     
  14. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I'm not making any points here, I was just verifying what I got from the video with the speed booster example. A FF 50mm has a bigger pupil than a 25mm on MFT, so it gathers more light and you can use a speed booster to make good use of it.
     
  15. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    Another error he made in this video is when he's comparing angle of view between 2 formats. Problem is, he's comparing it AT THE WRONG DISTANCE! It's a common mistake again made by a lot of experts.

    The focal length of the lens designed for each sensor size is determined and calculated with a subject at "Infinity". At least, this is used by almost ALL manufacturers. The angle of view of a 25mm on MFT is equivalent to a 50mm on full frame when the subject matter is at "infinity". The model shots don't look focused at infinity at all. It wasn't shot at infinity; therefore they may not have the SAME angle of view and that is due to the design of the optics of the lens and he may have to crop to match it.

    Nikon USA website has an excellent primer on this, comparing 3 of their telephoto zooms, the 70-300VR, the 70-200VR 1 and 70-200VR 2 lenses. At infinity and shot @ 200mm, they all have the same angle of view. But when shot closer, they all have a different angle of view; some tight and some not. This is due to their inherent optical design.
     
  16. GFFPhoto

    GFFPhoto Mu-43 All-Pro

    Feb 24, 2013
    Yes, more light passes through to a sensor with more area. A m43 lens with a pupil half the size will be spreading that light to a sensor with roughly 1/4 the area. What matters for exposure is how much light hits each pixel in the sensor, not the absolute amount of light passing through or the size of the hole. Absolute light transmission, or "pupil size" is kind of meaningless without looking at the area that light is spread to. I hope that explanation was clear, people seem to have a hard time wrapping their head around this, and it leads to goofy videos like this one.

    This guy also seems to be confused about the difference between field of view and focal length.
     
  17. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    Maybe it is because I and the guy in the video are NOT talking about exposure...
     
  18. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    The ability for a full frame sensor to have the ability that 2 stops advantage compared to a MFT is due to the size of the pixel well and nothing to do with the f-stop of the lens itself. And that 2 stops ONLY apply to the current full frame sensors like that on the 6D or D600/D610. A little better on the D4s and Df and possibly the new Sony A7s. The current Sony 16Mp sensor that's in the newer Olympus bodies have similar performances or better compared to the older generation full frame D3X and the Canon 5D Mark 1. Even my E-P5 is comparable against the older Nikon D700 or D3, not the D3s.
     
  19. zap

    zap Mu-43 Veteran

    215
    Jul 23, 2012
    uk
    as i've said in the other thread... not watching the vid!! :mad:
     
  20. zap

    zap Mu-43 Veteran

    215
    Jul 23, 2012
    uk
    now, where's the 3rd thread?