Quote Originally Posted by Stew View Post
Would closing the lens down to a smaller aperture help?
Perhaps. You can use the view camera focusing method with an enlarger. Jeff Conrad derived some equations that allow you to figure the maximum tolerable F number based on the MTF (personal correspondence).

N_max ~ 20 / (1 + m) sqrt(dv)

N_max = maximum tolerable F number
m = magnification
dv = distance on the enlarger column between good focus on the highest and lowest portions of the curved or askew negative. (if 'dv' is zero then your negative is not curved or enlarger/baseboard/easel is not askew)

I'm curious as to what your 'dv' is. In terms of 4x5, I find that it is just a few millimeters, as the 4x5 film tends to hold pretty flat even in a glassless carrier. If you are using 4x5 and you get more than a few millimeters for 'dv' then something is amiss, though stopping down may help.