Resolution, Print Size, Viewing Distance, 22MP
The great dispute about resolution seems to have got much more vigorous since we canon shooters ceded the MP crown to another make.
It's made me wonder whether there ought not be a reasonably scientific way of determining how much resolution is needed for most cropping and non-cropping purposes.
The ceiling for cropping is presumably the point where the lens limits the resolution at a certain amount of cropping so that it falls below "acceptable" for your purpose. I don't think we are there yet; and won't be until pixel densities on FF are above current APSC levels. The Other Brand is giving us something useful in being able to get some extra magnification out of our tele lenses without carrying a spare APSC body.
But what about non-cropping purposes?
Here it's trickier. Suppose for simplicity that it's possible to tell on print if the native resolution has been up-rezed (or printed at less than 300 DPI) on very close inspection. I doubt this is true for modest upressing, but let's assume it.
That gives us a very roughly 50 x 30 cm print.
This is a fairly large print. But notice I said "on close inspection". What will be visible will depend on viewing distance, and you aren't doing an artist any favours by looking at a print that large from 10cm away.
Let's further assume that with an ideal lens there is no more theoretically visible quality to be had for that degree of magnification.
Now the larger you print the more natural it is to view from further away (modulo the angle of view; for some purposes a wide angle view looks more natural closer up but lets set that aside)
The question is, does the best viewing distance fall away faster than the visible quality at close distances falls off? In other words, it's perfectly possible that at natural and sensible viewing distances the theoretically perceivable quality for a person with normal vision doesn't diminish at all after our 50 x 30 print - it may be that no increase in resolution will be visible from a an image which has natively more pixels than our image up-rezed.
And of course we might wonder how much less than 22 MP would do in the sense that up rezzing the even smaller pictures might not be visibly more detailed at natural viewing distances.
Anyway: what's the answer? Someone must surely have done the work (let's assume a subject with 20/20 vision. Is that what Pop Photo's SQF figures mean?