I know.
This theoretical approach is a too simplistic representation of the actual situation.
Those boundaries are already taken into account in reality.
Keep in mind to (as explained more early), you have to keep track by the real possibilities of what lenses can resolve itself.
To have benefit of 60 MP sensors, at least you do need lenses that can out-resolve the more tiny pixel dimensions.
Many / most lenses
don't. Even used at more wide aperture values.
Not to speak of these "super" zoom lenses. Starting at low open aperture values.
At "pixel peeping" observation, an image is not sharp any-more in front and behind the actual field of focus.
If the the blur scattering due to out of focus areas is already larger than the pixel dimensions itself,
(keep in mind that happens already very quickly at high pixel densities - and at pixel peeping enlargement).
The effect of higher pixel density is already lost due to much greater blur outside the field of focus.
So only for the relatively very small areas that are still imaged sharply with a 60 MP sensor,
(using top nodge quality lenses), you "can" still have "some" benefit from it.
No, that isn't true.
In my photography history, I've often shot on film, in formats up to 4x5 and 8x10 inch film sheets.
The resolution of film sheets itself exceeds
far - far the limitations of lens diffraction.
It was always a matter of finding a balance between the most optimal technical camera settings (tilt/shift),
the aperture used, in relation to depth of field, and used case as for enlargement.
And importantly, the blur caused by diffraction of lenses.
Keep in mind that with technical camera lenses, aperture values can be set (for reasonable depth of field reasons),
that extend
far the practical limits to maintain "any sharpness" at all, by diffraction reason of lenses
ONLY.
E.g. most technical lenses in those days you can set apertures values as small openings up to
F64
For 8x10 inch lenses even to
F90
By every diffraction calculation list, everyone will be amazed how little sharpness you have left.
But in that time we didn't use a diffraction calculation list.
Just real practice. So for critical work trying to go no further than 1.5 - 3 stops below "full wide" opening.
Technical lenses full wide openings start at e.g. F4.5 - F5.6 - F 6.3
But also do have (still) one APO design "reproduction" lens - 480mm - starting at F 9.0
Judging the "positive" slide film sheets on a "light box", by use of a high quality offset printing magnifier,
which normally allows you to determine the "printing grid / dots". You can see every deterioration.
Today’s digital camera's:
Just a comparable story as within those old "vintage" history, as it comes to the practical usefulness by the effect of diffraction,
in relation to resolution / pixel size.
By practise, no matter what lens is used, in my experience using the Panasonic S1R = 47 MP
the drop-off in sharpness due to diffraction starts at about F8 - (F7.1 do have the better sharpness overall).
The advantage today is that you can "mask" many lens faults and errors by post processing algorithms,
to tweak images in such a high level, that you can have the "impression" (a human "perceptual" experience),
that you "think" to see more detail. But in reality isn't. The real boundaries also have been determined today.
These today software advantages, can help to still use more small apertures, like F 11 as for DOF reasons.
To have the impression it is not that different by "perceptual" experience, to the better detailed image done at F 7.1
Or maybe even a better
real detailed image
at focus point area made by using e.g.
F 4.0 or F5.6
As that is the best performance of a lens itself.
The deterioration of sharpness by the effect of diffraction, and using more high pixel count sensors,
Lens factories are developing more fast lenses, e.g. starting at F1.2 or F1.4 at a more high quality level.
For the better aperture values about two stops aperture closed, to reach the best lens quality.
To meet as close as possible the borders by a more high sensor count.
I have to search to a diffraction calculated list, to see if this statement is valid. (I don't have it at hand now).
But I guess much of today’s M43 camera's / sensors are helped by today's software algorithms to "mask" errors.
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