For what's it's worth...just finished making a fresnel, actually cutting down a page magnifier I bought at office depot.

Tried several different methods of cutting the plastic, the only one that worked was to clamp a straight edge where I wanted the cut, and repeatedly scoring it with a utility knife until it broke.

Image is noticeably better, still dim mind, but much better. I think I can see well enough to compose accurately which I couldn't do before.

Thanks for all the helpful info, the Renner book is on it's way. I was told that pinhole photography is the gateway drug to alternative processes, which is why our department head makes pinholes out of coke cans...

JD