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conquering diffraction

Discussion in 'Native Lenses' started by kevwilfoto, Jun 30, 2012.

  1. kevwilfoto

    kevwilfoto Mu-43 Veteran

    294
    Sep 23, 2011
    Colorado
    I've ranted and raved against how narrow some :43: usable aperture is, usually because it's a zoom with f/5.6 (or higher!!) at the long end and diffraction setting in at f/8 (or earlier!!).


    The Panasonic 12-35/2.8 seems to be as flexible as the Oly 12/2.0, so the zooms are improving, but the prices sure are going up! :)

    Maybe it's *just* a zoom thing? Olympus seems to have resoundly beaten this f/8 diffraction ceiling with their 45/1.8 and 75/1.8. If Olympus does produce the rumored 25/1.8 or 17/1.4 those will be very desirable indeed. (I'm a zoom kind of guy, but I catch myself buying primes when I'm not paying attention, so either of those might accidentally make it into my bag.)

    Another rant slips through my fingers. :biggrin:
     
  2. CUB

    CUB Mu-43 Veteran

    275
    Apr 19, 2012
    The aperture at which diffraction begins to be a problem is dependent on the focal length of the lens.

    I was taught (admittedly some years ago) that diffraction became significant when the size of the effective opening of the diaphragm reached a certain value in millimetres (or a fraction of an inch). So a lens with a longer focal length will only begin to suffer significantly from diffraction effects at a larger f/number (smaller relative aperture) than a lens with a shorter focal length.

    Therefore I am not in the least surprised that, with the Olympus 75mm lens, significant diffraction effects have not yet set in at f/16 and only begin to appear at f/22. I also shoot large format where diffraction only becomes significant at f/32, f/45 or f/64 depending on the focal length of the lens I am using - obviously, the focal lengths are much longer than in m4/3 for comparable angles of view.
     
  3. s0nus

    s0nus Mu-43 Veteran

    424
    Dec 13, 2010
    Chicago
    Your rant is timely.

    I've been looking into improving my landscape photography, and have discovered that most of the photos I aspire to are shot sometimes at f22. I have also read that m43 gear performs particularly poorly in at super small apertures due to diffraction. On the other hand, I have pushed my Oly 14-42mI to f10 with personally acceptable results.

    It seems that I have to accept this limitation of the m43 system while keeping in mind that it's the size of my camera that allows me to carry it to places worth capturing.
     
  4. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    One shouldn't get too worked up over diffraction limits. Yes, at small apertures sharpness will start to decline, but it's not precipitous, and it doesn't mean that at f11 your pictures are great, but at f16 they look like they came out of a Lomo.

    It's entirely possible to get very good pictures from m43 at f22. You might want to apply a little extra sharpening, but if you need f22 (or 16, or whatever) to get the DOF you want, go ahead and take the shot. You might be surprised just how good it is.

    There are way too many people who are more concerned with test charts and theoretical limits than they are photography, and they all seem to gravitate to online forums.

    DOF is also related to the size of the sensor. So if the shot you're looking at was shot at f22 on a FF camera, you'll get the same DOF on m43 at f11 (assuming you're using a lens with the same FOV, and shooting from the same distance). If the f22 shot was on medium format (which a fair number of landscape shooters use), you'll get the same DOF at even wider apertures on m43. I suspect you'll rarely need to stop down to f22 to shoot landscapes on m43.
     
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  5. MajorMagee

    MajorMagee Mu-43 All-Pro

    Feb 24, 2011
    Dayton, OH
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  6. kevwilfoto

    kevwilfoto Mu-43 Veteran

    294
    Sep 23, 2011
    Colorado
    I believe you're correct. I believe some other aspects of lens design also factor in to controlling loss of detail due to diffraction. For example, the Canon 70-200 family has different diffraction characteristics, depending on whether you're using the f/4L, the f/2.8L, or the f/2.8L II, but all have the same focal length(s).

    I think this might all be due to the use of ultra-low diffraction elements and multi coatings. My 14-45 only has one aspherical element - it's sharp but only until f/8 or so. The Oly 75 has 5 fancy elements and a low diffraction coating. The 45/1.8 and 12/2.0 are similar, and have much better diffraction-free range than kit zooms. Focal length plays a part, probably because making fancy elements is easier/cheaper for longer lengths.

    This is a new era of :43: lens gear, pro-level image quality and correspondingly higher prices.

    I'm with you, and it's a decent trade-off to make. To me, the fact that pro-quality glass is coming very soon means that I made the right trade-off.

    Ugh, I think I just talked myself into the 12-35.
     
  7. arentol

    arentol Mu-43 Veteran

    269
    Jun 29, 2012
    On M4/3rds F/11 gives the same Depth of Field as F/22 does on 35mm. Diffraction also has the same relative impact at F/11 on M4/3rds as it does at F/22 on 35mm.

    The real difference is your ISO and shutter speed settings because your aperture is wider on M4/3rds. If you are going for a slow shutter speed on purpose then 35mm is better. If you want a faster one though, then M4/3rds is clearly better.
     
  8. kevwilfoto

    kevwilfoto Mu-43 Veteran

    294
    Sep 23, 2011
    Colorado
    @meyerweb There is a lot of wisdom in your post, and it is much appreciated! Although, I have seen some lens reviews that made it sound like you'd be crazy to touch XYZ lens past f/11 (for example). Overly hyperbolic and dramatic? Quite likely.

    Interesting that you bring up depth of field and equivalencies. So my f/5.6 kit zoom example is like a FF lens with f/11-f/64 but diffraction starting at f/16? The math is probably wrong, but I hope it conveys the thought well enough.

    Yes, we can be too dogmatic at times. "I always use base ISO." or "I'll never go over f/11." or "I always shoot at 1/125th or faster". I think learning the strengths and weaknesses of our equipment can help us make trade-offs in the field, as long as we don't get too dogmatic about those weaknesses.
     
  9. MajorMagee

    MajorMagee Mu-43 All-Pro

    Feb 24, 2011
    Dayton, OH
    Your lens and camera can make things worse, but they can never do better than the diffraction limit. For most of us the diffraction effect goes practically unnoticed.
     
  10. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    This is the real solution.

    The smaller 4/3 sensor is a HUGE advantage if large DOF is desired. I can't imagine needing f/22 on m43 in a non-macro situation.
     
  11. troll

    troll Mu-43 Veteran

    224
    Jan 25, 2012
    Is there any advantage at all, let alone a huge one? When large DOF is desired you close down the aperture as much as you can: for a 35mm camera with 24-70/2.8 zoom on it that would be f/22, and it's exactly the same for a mft camera with a mounted 12-35/2.8. But f/22 on mft would result in a lower resolution than f/22 on a 35mm camera, with diffraction on mft eating some if not all of the difference in DOF. What's more, 35mm sensors are just better in general, more resolution and larger photo sites, so the image from 35mm will be superior anyway.

    There are tests out there, for example Amateur Photographer did one some time ago, showing that in many (most?) cases shooting with the narrowest aperture doesn't make sense since whatever you earn in DOF you just lose due to diffraction, harming the whole image in the process. Macro is probably the only exception, and yet even with macro normal apertures and focus stacking are used as often as possible.
     
  12. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    The image from a FF camera may well be superior, for a number of reasons, but you've missed the point of my (and other) posts. If f22 on a FF camera gives you the DOF you need, you wouldn't need to stop down to f22 to get the same DOF on m43. You'd only need to stop down to f11. Yes, 35mm at f11 on m43 will give the same DOF as 70mm at f22 on FF*. The idea that you "stop down as far as you can" displays a lack of knowledge and understanding.

    * Approximately. It actually is more complex than simply using the crop factor, but it's close enough for discussion.

    And, if the FF and m43 sensors have equivalent resolution, in MP, then f11 on m43 will suffer the same level of diffraction as f22 on the FF camera.

    Your statement that m43 will suffer more from diffraction than FF really isn't accurate.
     
  13. MajorMagee

    MajorMagee Mu-43 All-Pro

    Feb 24, 2011
    Dayton, OH
    Sorry, but for green light (550 nm) the size of the Airy Disk is

    f Stop = Airy Disk
    1.2 = 1.6
    1.4 = 1.9
    1.8 = 2.4
    2 = 2.7
    2.8 = 3.7
    4 = 5.3
    5.6 = 7.5
    8 = 10.7
    11 = 14.7
    13 = 17.3
    16 = 21.3
    18 = 24
    22 = 29.3

    That relationship does not change because of the format of the camera or the focal length of the lens you're using. The only thing you can change that will make the values any different is the wavelength (color) of the light.
     
  14. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    ... And since you're at f/11 instead of f/22, you can take advantage of faster shutter speeds or lower ISO that can more than make up for the sensor difference.

    In actual fact, there may be even more advantage to going to an even SMALLER sensor if you frequently "need" tons of DOF.
     
  15. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    No, the size of the airy disk doesn't depend on the format, but it's effect on sharpness does. Well, more accurately, the effect depends on the pixel pitch of the sensor, and smaller sensors generally have much finer pixel pitch than do larger sensors. Not always, of course; a high resolution FF sensor, like that in the D800, probably has a finer pitch than the 12 MP m43 sensors. But if you assume similar MP counts, a larger sensor will have larger pixels, and a greater pixel pitch, than a smaller sensor.

    That means that an Airy disk of a given size will cover more pixels on the smaller sensor, and have a greater effect on image sharpness.
     
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  16. MajorMagee

    MajorMagee Mu-43 All-Pro

    Feb 24, 2011
    Dayton, OH
    Exactly, so the OM-D can really only take advantage of it's higher resolution sensor relative to the earlier m43 cameras at relatively open (f 5.6 or less) apertures. After that the size of the Airy Disk will limit them all to about the same amount of resolving power. It might have more pixels but there's not any more information coming from the lens than what the 12MP cameras can capture.
     
  17. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    No, no, no. Assuming similar sensor resolution, diffraction on the OMD will be exactly the same as a FF camera at the same DOF. Exactly. The. Same.

    To repeat: 35m at f11 on an OMD will have the same DOF, and the same level of diffraction, as 70mm at f22 on FF.

    You can keep trying to claim that m43 is inferior, but the facts don't support the conclusion you're trying to reach with them.
     
  18. NJH

    NJH Mu-43 Regular

    164
    Mar 8, 2012
    South West England
  19. troll

    troll Mu-43 Veteran

    224
    Jan 25, 2012
    And if f/22 on a FF camera doesn't give the DoF you need—then what? I still don't see any "huge advantages" of mft over 35mm when large DoF is desired.
    :confused: In practice with current cameras and lenses it is accurate. The smallest aperture most lenses have is f/22 for both mft and 35mm lenses, and at f/22 mft will suffer from diffraction more than FF.
     
  20. heli-mech

    heli-mech Mu-43 Top Veteran

    959
    Mar 9, 2012
    Vancouver Island, Canada
    Andrew
    I think the advantage comes in handheld situations. If you are shooting a scene with the same field of view that requires 1/FL F8 on both a FF and m43 then the m4/3 will have the deeper DOF advantage.
    Example:
    -FF 50mm @ F5.6 focused at 15ft will have 9.6ft DOF (3.4ft before 6.2ft behind)
    -m43 25mm @ f5.6 focused at 15ft will be past hyperfocal so everything from 7ft on will be in focus.
    (got these numbers from a phone app, please advise if any errors)

    Now the farther off you are focusing it will become less of a issue, or if you are shooting with a tripod, but under some circumstances there is a real advantage to m43 in terms of a deeper field. Just like under some circumstances there is a real advantage to the shallower depth of field offered by FF.
     
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