how to find best FX camera to avoid diffraction at small apertures

Question

Long time Nikon user. Looking to capture highest resolution images at smallest apertures possible in order to obtain most depth of field.

Have read various scientific writing about diffraction and while I get the basics (Huygens-Fresnel principle, Airy disk etc) feel blinded by science when trying to get simple answers of how to find optimum sensor resolution and pixel size to avoid diffraction, or even whether these are the determining factors in choosing the right kit.

Not looking for recommendations for particular camera(s) as other factors involved.

Answer 1

This is only possible by a system that corrects for the effects of diffraction in post-processing. For example Canon's Digital Lens Optimizer can somewhat negate the effects of diffraction. I'm not sure if similar features are available for Nikon.

The problem here is that by fixing the sensor size to full frame (36mm x 24mm) and by fixing the resolution to some high value, and by wanting to use a small aperture, you are creating conditions that invariably cause diffraction. No lens is going to eliminate it. No camera body is going to eliminate it.

The only ways you can reduce the effect are:

• Reduce the amount of diffraction using sophisticated algorithms in post processing
• Use a lower resolution
• Use a bigger aperture, however that creates shallower depth of field
• Use a bigger format sensor, however that not only costs a lot but also creates a shallower depth of field, unless you use a higher aperture f-number in which case you are back where you started with respect to diffraction and depth of field, but you definitely are not back where you started with respect to total system cost

Focus stacking might also help if your subject doesn't move and you can take multiple pictures using a tripod from the same position.

By the way, for landscape photography this is not a problem. For example 50 megapixels with full frame mean f/8 is the limit where diffraction becomes visible. However this means diffraction when pixel peeping, not diffraction when viewing a reasonable size of print from a reasonable distance. If you print a 1 meter sized picture that is viewed from 1 meter distance, a circle of confusion calculator gives 0.008 mm circle of confusion with perfect vision. With this circle of confusion, if you focus 40 meters away on a 50mm lens, anything from 20 meters away to infinity is in focus with f/8. And you have room to use for example f/16 if you want some nearby tree to be in perfect focus -- the f/16 diffraction would probably not be visible in a 1 meter sized picture viewed from 1 meter distance with perfect vision, it would be visible only when pixel peeping. This f/16 would allow anything from 10 meters to infinity to be in focus.

Answer 2

Diffraction and maximum resolution are just opposite sides of the same factor, aperture size. For a given aperture restriction, the size of the airy disks will be the same regardless of all other factors.

However, DoF in relation to diffraction/resolution is more of a trade... When you increase the DoF by using a smaller aperture you are trading resolution of smaller details in a smaller zone for a larger zone of resolution of larger details. And quite often the loss of fine detail matters much less; if at all.

There are also other ways of increasing DoF w/o increasing diffraction; such as using a smaller sensor with a shorter lens or from a longer distance, using hyperfocal distance, etc.

And, in terms of recording the maximum image resolution, the quality of the lens and user technique typically plays a much more significant role than sensor resolution does... Many struggle to record even 10MP of actual resolution, and you don't need more than 14MP in most situations; because you can't see it in an image viewed "normally" (but that's not to say there aren't other benefits to using a higher resolution sensor; there are).