Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Diffraction has absolutely nothing to do with any possible optical corrections - and it is consistent across focal lengths, lens brands etc. A Leitz mm lens used at F22 will produce the same detail loss due to diffraction as a more modestly priced lens. As a photographer who shoots landscapes, I can say without hesitation, that Peterson's advice is not as sound as it should be, and trading off image quality for depth of field doesn't work as his advice is suggesting, especially with cameras like the high resolution D8XX series from Nikon. I would have no qualms about using F22 on a 12 mp D700, however.

You may want to test this yourself and post the results.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

And the new tech in Adobe ACR - Super Resolution which actually works on Raw files for results superior to AI, Interpolation, Fractal and other kinds of "up-rezzing" tools.

https://www.youtube.com/watch?v=glxosZiBC6c

It was released today, and just might be a game changer for increasing image resolution in megapixel count, while preserving and actually enhancing fine details, using very high frequency microcontrast adjustments.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

I'm pretty sure this is what I understood from what you wrote. But I think there are some assumptions being made that may not be completely accurate. Focal length (angle of view at the entrance pupil) does not change as you increase magnification as you move the lens further away from the sensor - and that would not change the Airy Disk size anyway. I will suggest that nearly all lenses made today are internal focus type and subject to varying degrees of breathing due to the lens designer choosing to reduce focal length at minimum focus distance.

What you are referring to in your "effective aperture" is really only a change in light transmission as the lens is moved away from the sensor plane - it is not a change in any of the factors that affect diffraction. I sometimes use my 85mm F2.8 PC-E, which is not an internal focus lens, which changes light transmission from F2.8 to F4.2 at minimum focus distance and max aperture. It is still an 85mm lens, the angle of view doesn't change (even though a different focal length alone would not affect the Airy Disk Size resulting in different diffraction results), and the calculated Fstop doesn't change, therefore there is no change in diffraction, as you are suggesting. If I set this lens to F8, the meter reports it is only seeing F12 and will use that to calculate the exposure. But the diffraction will not increase because of the lower amount of light - the opening in the lens relative to the focal length remains the same - as does the Airy Disk size.

Thomas902 Loc: Washington DC

Thanks Gene...
I read your post in the Super Resolution thread... and looked at dpreviews article you linked to...
https://www.dpreview.com/news/0299184261/adobe-releases-photoshop-for-m1-macs-and-introduces-super-resolution-in-acr

Very interesting what enhancements software can achieve in perceived acuity...
Albeit shooting at a lens' optimum aperture goes a long ways to maximizing acuity in my humble estimation...
For my client work I live between f/8 and f/13 depending on the optic.
However for sports I'm nearly always wide open.
DxOMark does a stellar job of scoring an optics performance at various apertures.
I've been very pleased with following their results...

Thanks again Gene for stay abreast of current industry trends.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Totally agree!

I didn't have to go to F22 to get stars. F10 is fine, and so is F6.3 as one can see below.

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F10

(Download)

F6.3

(Download)

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

This is only valid in proper context. Detail that exists but is not captured - aka "lost" - but expected to be there, is very much an issue, at least in some circles. In general, lens designers, camera manufacturers, tripod manufacturers and the majority of photographers would not agree with your statement.

petrochemist Loc: UK

Yes diffraction can be a problem, it's very noticeable on some of my longer focal length set-ups. At normal f-stops it's not a significant issue, but if you stop down to f/64 you don't need pixel peeping to see the effect.

wdross Loc: Castle Rock, Colorado

Great night shots. Especially like the second one for the mood generated.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Thanks!