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Thread: Diffraction

  1. #1
    Super Moderator Kayaker72's Avatar
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    Diffraction

    Bryan just posted the ISO charts for the Sony a7RIV. In his post, he referenced comparing diffraction at f/8 vs f/11. And, yeah, I can see it, mostly in the center, but it is so slight at 100% at 61MP, I have trouble thinking of an instance where I would pick f/8 over f/11 here.

    Taking that a step further, you can start to see diffraction really set in. Here is a more extreme case of f/4 vs f/16. Ok...that is pretty noticeable. But I also try to think with 61 MP, get away from pixel peeping....f/16 is probably still a very good image and it would take some effort to notice it isn't as sharp as the f/4. Maybe something that has fine contrasty lines.

    At least that is my thought. I haven't tested side by side, but I sometimes shoot some scenes f/16, even f/22 and do not ever recall regretting that decision. Of course, I am f/5.6-f/11 usually when I want the sharpest image.

    Anyway, just something I thought was interesting. Have any of you ran into a circumstance where diffraction impacted an image?

  2. #2
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    Yes. It always seemed to come in to play with macro with narrow depth of field.
    Seldom with wildlife because the battle is always for more light so rarely do I get over f/8.
    Landscape when I go above f/11 the situation is usually one that critical sharpness isn't as important.

  3. #3
    Super Moderator Kayaker72's Avatar
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    All that makes sense. I should have also clarified, I was thinking of landscapes as that is the majority of the time I stop way down. If I shot more macro (I hardly shoot any), I could certainly see it becoming an issue.

  4. #4
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    f16 at 61 mp is sharper than f16 at 30 mp even though both are diffraction impacted.

    goes along the same line and over all system MTF function.

    Also makes the case for very good T/S lens (I love my mk 1 90 mm) to align the focus plane w/ the desired DOF.
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