I asked this in the context of another thread
I may not be explaining this the best way (that's why I take pictures...)
I'm not sure if it's entirely an perception/optical illusion, or whether there is some math behind this, but:
When someone says "I'm thinking of moving up to 8x10 and schlepping that around the countryside because I like the idea of a big neg" people on here often say "why bother with 8x10 unless you really want to do contact prints, just use 4x5 if you are going to enlarge" or words to that effect
Apart from the differences if you are going to print big - 4 or 6 feet wide - which is another issue - I feel there is a real difference in look or perception between the same scene taken with an equivalent lens in the two formats.
That is, suppose you photograph the same landscape scene in 4x5 with a 125mm lens and in 8x10 with a 250mm lens.
Pretty close equivalents. But to my eye the scenes are rendered differently.
I know I always get a little lost with the math and different DoF from one format to another and technically how the difference between a 125mm on 4x5 and a 210mm on 8x10 pans out. But even using movements to bring everything into focus from front to back in both photographs, to my eye there is a different perception of the space in the two images.
Maybe it's an optical illusion? Maybe there is some math behind it? But my personal feeling is that photographing the same space using the two different formats (with equivalent lenses) gives two differing perceptions of that same space.
Or am I completely wrong, and grain aside, if you took the two identical photographs with the two formats from the same spot using lenses that were equivelent in angle of view, blew them both up to say 20x24, visually, perceptually, they wouldn't look any different?