Quote Originally Posted by Andrey View Post
I'm just curious what you think in terms of the difference in the circle of confusion and critical focus. If I'm printing my negative and don't use a piece of paper under the grain focuser, would by focus be significantly off? Would it matter at all, considering the negative is not flat, but bent just slightly anyways?

What is your opinion?
I don't have an opinion on the matter, just the optical formula that predicts about a 2mm focus spread at f2.8 at 9x enlargement. This easily encompasses any photographic paper of which I am aware.

Modular transfer function focusing equation (equation #38 in http://www.largeformatphotography.in...DoFinDepth.pdf) :
N_max ~ 20 / (1 + m) sqrt(dv)

N-max = F number
m = magnification
dv = focusing leeway on the baseboard
20 = constant for circle of confusion about 0.15mm on the print