Quote Originally Posted by hpulley View Post
I'm trying to think if you'll have 8x narrower DOF at 8:1 or more than that. If it is 8x narrower will it be less obvious in a contact print than the required 8x enlargement of a 1:1 image? Is there a nonlinear factor which won't come out in the wash?
If the final magnification is the same, DoF is too.

There isn't enough DoF anyway, so an 8x reduction of it may sound pretty impressive, 1/8th of nothing isn't significantly less.

Quote Originally Posted by hpulley View Post
Grain and tonality will be better on the larger piece of film. If the other factors can be practically overcome then the larger format should win but can you buy or make an 8:1 setup for an 8x10 camera?
Yes, you can. You just don't use a 210 mm lens.

You typically use very short lenses (i use 16 and 25 mm lenses mostly) when in-camera magnification gets beyond 3 or 4x life-size.

It's not just grain and tonality, but also that - because of the larger in-camera magnification - you resolve more subject detail. Enlarging an image recorded on a bit of film will not increase the amount of detail you see in the subject, just enlarges what you have captured on it at that lower magnification. Get to the same size magnification on film, and there will be more detail in the captured image.