Quote Originally Posted by Newt_on_Swings View Post
Also did you place a sheet of paper under the finders the same thickness of the paper you are printing with?
We busted that myth a couple of years ago. I contacted some manufacturers of grain focusers and the conclusive view was that it doesn't make any difference.

The depth of focus at the paper is quite large whereas the position of the negative is very critical. You cannot move the negative with respect to the lens with enough precision to make any difference as small as the thickness of paper.