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Fred Miranda wrote:
Diffraction starts as soon as you stop down from a lens's widest aperture, but it’s usually not noticeable at wider apertures like f/2.8 or f/4 with current sensors, even those with 60MP. At pixel level, it becomes visible only at smaller apertures like f/8 and beyond.
To achieve the best optical performance, stopping the aperture down about 2 stops from wide open to reduce most aberrations, but with high-performance lenses like Cosina's APO-Lanthar or Leica SL APO, only one stop down might be sufficient due to their apochromatic design..
While I think it's wise to avoid apertures smaller than f/8 in most scenarios, there are cases where using f/11 or f/16 is necessary to achieve a broad depth of field. Deconvolution sharpening can help recover some sharpness lost to diffraction. Another option is focus stacking, although it requires multiple shots. For landscapes with a prominent foreground element, a good approach is to take one shot at f/16 or f/18 focused at the lens’s hard stop (infinity) and another shot at f/5.6 focused on the foreground element. Combining these shots in post-processing can achieve sharpness throughout the image, with high-frequency detail and micro-contrast in the foreground which is usually the primary focal point anyways..
It’s often better to have the subject in focus, even if slightly less sharp, than to risk missing critical details, similar to using a higher ISO for a sharper subject despite increased noise....Show more →
Great explanation, thanks very much!
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