I have 10 years experience in masking 35mm (profesional lab)in germany. 1. dont produce the mask in contact; use one camera to do one 1:1 copy for the mask. (dust) 2. develop the film / mask. 3. mounting the negative and the mask, best in one dia-frame (with glas) or with one paper on side (for handling) More information and adress, send e-mail!(posted 8458 days ago)