The misconceptions brought up by new lens introductions

Discussion in 'Olympus Cameras' started by RichA, May 24, 2012.

  1. RichA

    RichA Mu-43 Regular

    Mar 28, 2012
    "You have a 100mm f2.8 lens on a 4/3rds? So what, it's only = to a 200mm f5.6 on a FF!" We hear stuff like this a lot. It's only partially true.
    This happens every time a new prime is introduced for m4/3rds.
    The equivalency thing only applies to angle of view, nothing else.

    The lens on the 35mm sensor isn't "faster" but the sensor may be more sensitive. A 12mm lens on a 4/3rds sensor gives the same angle of view (imaged area) as a 24mm lens on a 35mm (notice I didn't say full frame, because the 35mm format is a hoary old format from early film days?) format camera.

    The physical sizes of the lenses will be different, but because of the way wide angle lenses are designed (some have huge front elements, etc), it's best to use example lens focal ratios and focal lengths on longer lenses, to get an idea of how each aspect of gear impacts physical size.

    We take a 100mm f2.8 lens on a 4/3rds and a 200mm f2.8 lens on a 35mm format, you get the same angle of view if the cameras are at the same distance from the subject. The lens speed is the same and you'll see the same image density (more or less, at a set ISO) from both cameras if the aperture and shutter speed are the same. What will be different physically will be lens size.

    Roughly speaking, lenses of double the focal length and the same speed as another lens will be twice as large, the diameter of the optical elements or the "clear aperture" must be twice as wide because focal ratio is focal length divided by optical element diameter at its widest or "clear aperture." So, a 100mm lens of f2.8 is going to need a clear aperture of at least 36mm while a 200mm lens of f2.8 focal ratio will need a lens aperture of 2x that or 72mm.

    The qualifier here is that sometimes manufacturers use a larger front element than needed to avoid certain image aberrations and physical flaws the lens might have. Thus, a lens that provides the same area coverage and speed on 35mm as a lens that does on 4/3rds is going to be roughly twice as large and probably 2-3x as heavy because the lens elements are (by area) much larger. This will vary given glass types used, element number, housing, etc, but again, wide angle lenses have vastly different designs so may not adhere completely to this rule.

    Does the lens with the larger clear aperture gather more light? Yes, light collection is solely determined by lens surface area, but since you are dividing that light over an equivalently larger surface area (the light cone encompassing the 35mm sensor) it provides no additional light at the sensor IF the pixel density is the same as the 4/3rds sensor, and if the aperture and shutter speed is identical.

    But, IF the pixel density (the pixels are larger) is not as high in the 35mm sensor as the 4/3rds, then each pixel IS getting more light in the 35mm sensor. Right now, a 4/3rds sensor with 16 megapixels has a much higher pixel density (pixels are smaller) than a 35mm sensor with 24 megapixels, so each pixel in the 35mm camera gets more photons. In fact, there are no 35mm sensored cameras with pixel densities as high as a 16 megapixel 4/3rds sensor at this point.

    Maybe Canon will release a 48mp 35mm camera? The final image produced by either of those two sensors is dependent on a lot of other things, once the light hits the sensor.

    Arguably, the pixels in the less dense 35mm sensor are more "sensitive" (because they collect more photons by virtue of their larger size) which results in the better high ISO performance they show. The larger the pixels, the greater their "photon well capacity." But the end result depends on so many other things in the camera that the advantage isn't as dramatic as it might seem, except in the case of something like the Nikon D3s/4 which have huge pixels and very low pixel density and that sensor has fantastic high ISO performance.
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  2. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    RichA -- I want to read your post, but could you edit it into paragraphs. This is waytoomuchandtooclosetext. Could you edit it, to break it up a bit?
    • Like Like x 5
  3. st3v4nt

    st3v4nt Mu-43 Veteran

    May 26, 2011
    Jakarta, Indonesia
    Same here, although I may from time to time do the same thing in my post.
    The post a bit confusing to read.

    I wish 4/3 alliance will once and for all creating an explanation in animation
    infographic form to explain the 35mm and 4/3 equivalent of lens. Also the pixel
    density since I'm curious why 35 and APS only have 72 ppi density while m4/3
    always have 300-350 ppi in JPG.
  4. b_rubenstein

    b_rubenstein Mu-43 All-Pro

    Mar 20, 2012
    Melbourne, FL
    It is completely true for, because a 100/2.8 ยต4/3 lens gives the same FOV and DOF as a 200/5.6 FF. Wide open, the two lenses will give a different look.

    The larger aperture of the 100 passes more light, and would permit a higher shutter speed, or lower ISO setting, but that's often besides the point for a photographer going for a certain look.
  5. thazooo

    thazooo Mu-43 Rookie

    May 24, 2012
    Mississippi, USA
    Real Name:
    Dana F.
    Great Post. I've been watching all the negative comments regarding the m4/3 lens releases and was dumb founded by all the negativity from the FF crowd. Guess they need to justify paying sooo much for the

    I agree with everything you've posted and find the argument about how much better FF is over all other formats ridiculous. I think most of the argument centers on DOF and when you run the numbers on a DOF calculator, there's not that much of a difference. Light gathering is Null also, most of us don't shoot in a pitch black room.

    I'm a new user to this gear. 3 months into use and really enjoying the camera.
    I got the E-PL1 with Kit Lens and since I like Primes, grabbed the Sigma 19mm.
    I'm not seeing that much of a difference between the E-PL1 and my big body with regards to image quality. And I'm really enjoying shooting some JPG's and not having to spend time in PP.

    Let em' talk, we all know how capable these m4/3 are.

  6. silversx80

    silversx80 Mu-43 Veteran

    Apr 27, 2012
    North Carolina
    There are many misconceptions in the world of optics, CMOS/CCD sensor tech, and photography. The only thing that really needs to be understood is "do I like the results?" If yes, then great. If no, then you need to learn how to make it better.

    Everything else is mental masturbation.

    I want to amend this post with words of advice from Kai (DigitalRev):

    Don't be a bokeh-whore.
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  7. Luckypenguin

    Luckypenguin .

    Oct 9, 2010
    Brisbane, Australia
    Real Name:
    I think that DOF equivalence is one equivalence too far. I understand exactly what focal length equivalence means because the terminology is so widely used and many compact cameras even display equivalent focal lengths. DOF equivalence is (literally) a fuzzy concept and usually just causes disagreement and confusion.
  8. I think we could profit by some clarifications:

    Angle of View: Comparing 4/3-m4/3 lenses to 35mm lenses (I cannot apply FF to 35mm format either, recalling when it was looked down on as too small for quality work!), the 100mm (m)4/3 lens will have the same angle of view as the 200mm 35mm lens. This affects framing, of course, and the proportions of the sensor affect what kind of framing one might do, but the formal angle of view will be the same.

    Aperture: Apertures are ratios, and I believe a good deal of the hot air we project in these discussions involves not understanding the concept of ratios. 2.8 is 2.8. Since exposure for a given scene is usually bounded by: 1) ISO; 2) shutter speed; and 3) aperture. The two cameras set to the same exposure parameters for the same scene will yield identical exposures (within the tolerances of each metering system, etc.).

    Depth of Field: This is where things get stickier. In the theoretical situation of the two lenses on two different cameras set the same distance and to the same exposure, the depth of field will be different. This may or may not be very noticeable, however, or even objectionable, depending on the actual aperture chosen, the viewing distance of the finished photograph, and the personal taste of the photographer and audience.

    So, a photographer (Nikon Nik) with a 35mm sensor Nikon is out shooting with his buddy (Oliver Oly) who has a m4/3 camera, with say, a legacy lens of exactly half the focal length of the Nikon. They set their cameras on their respective tripods and focus. Oliver does not trust his metering for some reason. He gets Nik's parameters and sets his camera to the same ones (ISO/shutter speed/aperture). From the same vantage point they will get photos of the same exposure, no "adjustments" necessary. Framing will be somewhat different because of the "squarish" format of the Oly compared to the elongated format of the Nikon, but it will be the same otherwise. When they get home and load their files onto the computer for full-screen viewing, they will probably be able to notice some differences in depth of field, however.

    That is how I have understood things to operate. Please correct me if this scenario is incorrect in some way, however.
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  9. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    I've read the math, and seen the passionate debates about photons that always seems to show up. All I know is this -- when I had my 5D and my m43, I tested lenses, using the same framing by backing up 2X as far for m43, and found the blurriness of the background looked pretty dang close when I shot, for instance, a 100mm lens on the 5D at 5.6 (aperture opening of 100/5.6 = 17.86mm) vs. a 50mm lens on m43 at 2.8 (aperture opening of 100/5.6 = 17.86mm). I also tested other various lenses and various FL where I had matching pairs (also testing my APS-C DSLR at the same time, but that was harder to match).

    I'll leave it up to the math whizzes as to how technically accurate it is, but in practical terms, I found it very useful.

    Then, I went and looked at what aperture I shot my 50mm lens on my 5D, when I got results I really liked. Mostly it was at f/2.0-2.8. The PL25/1.4 gets close enough for me, and at a HUGE benefit in weight/size, and the Nokton is there if I wanted to get silly with it.

    That was enough for me!
  10. RevBob

    RevBob Super Moderator

    Jun 4, 2011
    NorthWestern PA
    Real Name:
    Thank you - this is very clear and simple to grasp. The numbers game always makes my head spin.
    In the end, it is the result that counts and that is very much up to the skill of the photographer - an intangible quality that cannot be measured and inserted into a formula. :biggrin:
  11. drewbot

    drewbot Mu-43 Top Veteran

    Oct 21, 2011
    Toronto, ON
    This very discussion is creating a wasteland of threads at DPR. People complaining they want "equivalent" 24-70 with the same DoF as FF, which means an f-stop of 1.4.
  12. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    Isn't that a tautology?? :biggrin:
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  13. Nate Crisman

    Nate Crisman Mu-43 Rookie

    May 23, 2012
    Another thing that is not being compared is the spacial distortion.

    Using the Mu4/3 sensor w/ a 100mm lens compared to a 200mm lens on a FX sensor, has anyone made a distinction of the effect of compression between subject/background?

    Does the 200mm/FX image have a more compressed space "look" even though the angle of view is the same as the Mu4/3?
  14. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    I'm planning, at some point, to create a FAQ forum here where we address questions like crop factor, DOF, diffraction, etc, in a systematic way.

    A lot of the "equivalence" squabbling at DPReview comes down to disagreements about how it is best to express things:
    • Focal length doesn't change between formats, but it is convenient to use an "equivalent" focal length to relate angle of view to different format sizes.
    • Relative aperture (focal length relative to physical aperture, ie f-number) doesn't change on different formats, but it is convenient to use an "equivalent" relative aperture to relate depth of field to format size if moving amongst multiple formats.
    • Where things get dicey is that people also use "equivalent" relative apertures to compare total light collection between various formats and then draw conclusions about image quality. On the one hand, it is true that the exposure (which is determined by shutter speed and f-number) is a major determinant of signal to noise per unit of sensor area, thus a larger sensor will make up for the effects of a lower exposure (higher f-number for a given shutter speed) when it comes to whole image signal/noise. On the other hand, the idea that total light collection is the only determinant of whole image signal/noise based on the assumption that sensors use equal technology, which often turns out not to be the case.
    From my standpoint, the major source of controversy in the DPReview forums is not that people have different beliefs about all of this. It's possible to discuss these issues without all the grief. Rather, the controversy comes from the fact that a few people with no interest in Micro Four Thirds whatsoever continuously patrol the MFT forum looking for every opportunity to explain how larger sensor size allows for better image quality. It's the most basic form of trolling.

    I've said it before and will say it again: If anyone comes on this site making it their life's mission to teach "equivalence", they will find themselves banned in a hurry.
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  15. InOmaha

    InOmaha New to Mu-43

    Feb 24, 2012
    Equivalence can be useful if you own multiple camera systems with different sized sensors.

    Equivalence is all but meaningless if you have one camera system with the same size sensor. It's better to spend your time getting a specific look AOV/DOF/Shutter speed, etc. by doing the same calculations you would have to do with any other system. Adjusting aperture, distance to subject, focal length, distance to background, lighting, etc. Then if you find you're too far back, limited on lens selection or cost, etc. you consider switching or adding systems or better yet create your own look.

    Anyone coming into this forum saying an f2.8 lens isn't worth it because it's really f5.6 is trolling. You buy a lens that works on the camera system you own or you don't. You learn to use added DOF to your advantage or you don't.
  16. WT21

    WT21 Mu-43 Hall of Famer

    Feb 19, 2010
    I'm coming around to the idea that we should start using AoV more. It would alleviate the different sensor size issue, and also I think I'd become more comfortable with the width of the scene I can capture in front of me.
  17. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Real Name:
    I think some of the problem is that there isn't much left to hold onto 35mm sensor cameras other than for DOF. I think thats where much of the clamoring comes in at.

    Originally mFT didn't have clean ISO to a certain level. Now it does, about as good as APSC. Then, there wasn't fast glass to reduce the ISO value needed. Now there is.

    What's the reason left for owners and users to hang on to those larger cameras? DOF. On a 35mm format camera, f2.8 for any focal length on mFT would require an f1.4 lens to get equavalent DOF out of mFT. A 35mm format camera can even achieve greater DOF with an f2 or f1.4 lens. Last I checked these lenses were large and expensive.

    If someone is looking for more DOF than the Olympus 45mm f1.8 can provide, I think that individual needs to move onto a larger format or wait for a 45mm or 50mm f1.0 lens to come out.
  18. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Real Name:

    Thank you. I think the discussion and understanding is important, but that is as far as it needs to go. Like I said in my previous post, if one is seeking razor thin DOF, there are cameras and formats out there for that. We here have accepted the benifits and limitations of the system.
  19. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Real Name:
    The problem with AoV is that even this gets dicey because the diagonal AoV is going to differ based on aspect ratio of the format.
  20. landshark

    landshark Mu-43 Veteran

    Apr 27, 2010
    SO CAL