OK last question, I promise! So I have this fancy contact printer with the 'split' hinged back. Supposedly, this is useful so that I can look at the PT print during exposure without losing registration. What exactly am I suppose to look for? I mean, I've read a couple books - well skimmed through them really - and read a couple different websites, but nowhere does it tell you what you're suppose to look for. Every reference was unanamous in stating to remember the exposure time for the UV source used. If that's the case what's the point of the hinged back? Thanks again, Art.