Hello Bob,
It is a bit confusing due to the use of some extremely low grain films, like Ilford Pan F 50 (B/W) or Fuji Astia 100F (colour transparency). Print images from these films at small enlargements, and the grain just is not there to be seen without a loupe. I usually find more texture in the paper than grain from the film.
If something were out of alignment in the printing process, then one or two corners might look different. However, in a case with defocused or monochromatic edges, and extremely low grain films, do you still find it easy to apply your test, or is there some other method you use? An example:
Dead Link Removed
Which is from Ilford Pan F 50. I had a great deal of trouble focusing the enlarger at all on grain, though focusing on edges of detail worked okay. I eventually had an 8" by 12" print made for my by someone I considered far better than I at producing B/W fibre prints, and the grain still was not evident to an unaided eye.
I have a few giant 24" by 36" B/W enlargements from 35mm TriX, and those would pass your grain test easily in the corners. Under glass one of those is really tough to see the grain, since the upper half of that image is black night sky, devoid of detail. I might imagine a high contrast image with corners as the white of the paper would also not show grain.
Normally I would look at the in-focus areas of a print to investigate the technical quality of an image, and often that detail might not be at the edges. I readily admit to not being a great printer, so I use well respected labs or talented B/W printers like Gene Nocon for my images. My colour fine art images come from transparency films, usually extremely small grain, and I am just not picking up on what you describe . . . . maybe on some images I can find what I think is grain on two or three corners, but any images with lighter areas of colour (especially 10" by 15" prints from 35mm Fuji Astia 100F) show nothing more than what was in the original scene.
However, if I place a loupe over the corners of those same images, then I can see grain amongst the texture of the paper. I have young eyes, and wear light power contact lenses, but I cannot pick up what you are describing without a loupe. It does not seem like you could take a loupe to many exhibits and actually get that close to someone else's images without attracting some bad attention to yourself.
Your long experience in business is probably partially responsible for your abilities, or what you investigate in the images of others. Where understanding your methods better could help would be to figure out how you are doing this. Since I rely on others doing my printing, this might help me evaluate my final prints . . . or maybe all my prints just suck? Thanks in advance.
Ciao!
Gordon Moat
A G Studio