Some types of film grain just seems to bounce more light at larger apertures. Then there are cases where one wants to be certain what they are focussing upon is the emulsion side of the film itself and
not the grain of an attached mask. Then different kinds of Newton ring glass bounce incident rays a
little differently with different lenses and diffusers. Sounds complicated in theory, but is pretty simple
if you just examine the image at more than one f-stop. I like to print color with a very shallow depth of field for all the above reasons, so want the widest aperture which bags the result. B&W printing is less
fussy unless an unsharp mask is also employed. And like I already indicated, one simply can't assume
a lens is devoid of focus shift - there are a lot of cheap lenses in use out there, and I sure as heck don't
intend to purchase and test a bunch of them. Gimme Apo Nikkors and Apo Rodagon N's and Rodagons
and Nikkor EL, whatever... just nuthin old or cheap (I do sometimes use a wretched old Carl Meyer process lens because it wonderfully complements certain soft portrait images, but that's a deliberate
tweak into oldie land).