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  1. #31
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by ic-racer View Post
    Here are two examples. An Olympus 50mm 1.4 SLR lens vs a Leica 50mm 1.4 rangefinder lens.
    Those seem to be especially thorough and well-done tests.
    I don't have either lens, but the results could seem to fit their reputations (Olympus over-corrected for outer edge?)

    Where can I find more?

    Best regards
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  2. #32
    Athiril's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    I checked my files. The RIT targets come in three different contrasts:

    32:1, 6.3:1, and 1.6:1
    It'd be interesting to see lens performance @ 1.6:1, rather than on typical charts, as well as interesting to see how the other low-contrast areas perform that you have there (6.3:1)

  3. #33

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    Lots of good points here. Need to be careful of terminology though. Any lens is always diffraction limited at its maximum aperture, since the Airy disk size is only a function of the aperture diameter. The best performance may be found at smaller than maximum apertures due to better optical correction by stopping down.

    To check the intrinsic resolution of a lens I used to use Kodak High Resolution Glass Plates (HRGP) that used a very fine emulsion capable of 2000 L/mm. For lithography applications we were interested in high resolution at the best contrast we could get since the HRGP plates were very high contrast emulsions. There are no equivalent modern emulsions to HRGP that I know of. For modern photographic purposes it is clearly more important to consider the film/lens performance as a unit as suggested by Ralph.

    Nate Potter, Austin TX.

  4. #34
    Athiril's Avatar
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    I'm waiting for the day that negative refractive index optical materials start being used by lens manufacturers... lens with resolution limited only by abberration, no diffraction limit, continue to stop down for ever sharper images

    They've already been used in the visible spectrum a few years ago.

  5. #35
    ic-racer's Avatar
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    Quote Originally Posted by Rol_Lei Nut View Post
    Those seem to be especially thorough and well-done tests.
    I don't have either lens, but the results could seem to fit their reputations (Olympus over-corrected for outer edge?)

    Where can I find more?

    Best regards
    After a quick search of the net, it indeed looks like the old Modern Photography and Popular Photography magazines do not have PDF archives. So this info is locked in these old magazines.

    I got that particular test from a special they ran on "32 Normal Lenses" back in the late 70s. Too bad they did not test the f1.4 Planar 50mm at that time. Later they tested a Contax and ran that cameras Planar 1.4 50mm individually. I can't find that one currently, but as I recall it was between the Zuiko and the Leica Rangefinder lens. I believe the Planar was very similar to the Leica SLR lens. I need to do some more digging.

  6. #36
    Rol_Lei Nut's Avatar
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    Quote Originally Posted by ic-racer View Post
    Too bad they did not test the f1.4 Planar 50mm at that time. Later they tested a Contax and ran that cameras Planar 1.4 50mm individually. I can't find that one currently, but as I recall it was between the Zuiko and the Leica Rangefinder lens. I believe the Planar was very similar to the Leica SLR lens. I need to do some more digging.
    I've seen many tests of the f/1.4 Planar (I even have one, collecting dust as I'm not really a 50mm fan...).
    It's usually not especially impressive in tests, but is a lovely and much admired lens in practice (low flare, lovely singnature and 3D look).

    Another example of real-wold impressions being just as important (or even more so) than tests alone.
    M6, SL, SL2, R5, P6x7, SL3003, SL35-E, F, F2, FM, FE-2, Varex IIa

  7. #37

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    Quote Originally Posted by Nathan Potter View Post
    Lots of good points here. Need to be careful of terminology though. Any lens is always diffraction limited at its maximum aperture, since the Airy disk size is only a function of the aperture diameter. The best performance may be found at smaller than maximum apertures due to better optical correction by stopping down.
    The Airy disk size may depend on aperture size only, but aberrations do not.
    In most cases, you can't reach the resolution limit diffraction alone would set, because the effect of aberrations is far worse when a lens is set to its maximum aperture.

    So almost no lens is diffraction limited at its maximum aperture.

    Stop a lens down, i.e. reduce the aperture size, and the effect of aberrations may (and usually will) reduce. But so will also the resolution diffraction alone would limit it to.

    The trick in stopping down vis-a-vis resolution is to stop down (i.e. reduce the aperture size) far enough to limit the effects of aberrations on resolution to the point where the result is equal to what diffraction will limit resolution to at that aperure size.

    Stop down further, reduce the aperture size more, and diffraction will take over as resolution limiting factor.

    So "Any lens is always diffraction limited at its minimum aperture".

    We must be careful of terminology.

  8. #38
    RalphLambrecht's Avatar
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    What Q.G. said.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #39

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    Quote Originally Posted by Sirius Glass View Post
    Thank you, that was well stated. The last paragraph hit home because I keep thinking about going into LF.

    Steve
    Don't forget about the increased ability to crop and get a better composition with LF which often results in better pictures. It's not all about lp/mm.

  10. #40
    RalphLambrecht's Avatar
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    Quote Originally Posted by domaz View Post
    Don't forget about the increased ability to crop and get a better composition with LF which often results in better pictures. It's not all about lp/mm.
    To compose during image taking or image making is a whole new conversation, but I fully agree with your statement about lp/mm.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

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