There are several factors affecting the disadvantage of diffraction and the benefit of depth of field. Very often DOF helps much more than diffraction hurts.
We rarely show 100% size, and typically resample tremendously smaller, so we typically have resolution to spare, allowing the beneficial tradeoff for greater depth of field. We are likely missing out if we don't investigate that advantage of depth of field. When it helps, it helps. And very often, stopping down more helps. We should use our heads, and try some things, and look for best results. If we don't look, we will never see.
Image object size is a factor. If the image object size is large, like half of the frame, it is easily seen and diffraction is a lesser factor... than if the tiny object size is comparable to an Airy disk size.
Increasing subject size can always help, in several ways, diffraction being one of them. Saying, there are vast numbers of line pairs of resolution across a large object, and few across a small object.
Lens focal length is a factor. The diffraction formula says f/d, which is fstop number, and a direct relationship. However, real world obviously says more f helps, and small d hurts. The longer lens certainly is a plus. A 24mm lens will not provide f/32, and probably not even f/22. But a 200 mm lens probably has f/32 and it is intended to be used (but an 18-200 mm zoom is in the wider class). Focal length is an advantage of the 105 and 200 mm macro lenses, allowing more extreme stopping down. We already know these things...
Pinhole cameras need at least about f/100 to even be usable.
Ansel Adams had his f/64 group, specifically to promote sharper more detailed photos in the day (1930s). But he also used a 12 inch lens (300+ mm) on his 8x10 view cameras.
There is a lot to be said for stopping down, but yes, less so on wide lenses. My view is at
Diffraction limited images? Really?
