Making the Film Positive
Use a basic black and white photographic enlarger to enlarge negatives onto the lith film. A condenser enlarger will produce slightly more contrast than a cold light or diffusion enlarger. A graphic arts copy camera is well suited to making enlarged positives because the lens sharpness and the flat film planes normally found in graphic arts equipment are far superior to those in the basic enlarger. Whereas enlargers can make drastic enlargements with a minimum of intermediate steps, the copy cameras are ideal for making sharp positives from large or medium format negatives. Another method of making positives from negatives is to contact print the negative directly to film. The only really important requirements here would be dust-free tight contact between the negative and the positive film and even illumination from a timed light source.