I put a small compact in various parts inside my 5x7 to check for light leaks and I believe one to be coming from the rear as I can faintly see the back of the lens at 15" f2.8 ISO 400.....what material is this and where do I get it?
I used velvet ribbon that I got from the fabric store, and either used spray-mount or hide glue mixed from Knox gelatin to glue it (don't remember which). The nice thing about the hide glue is that it's completely reversible.
100%. Any light from any source between the lens board and the film surface will be recorded on the film either as an image or as fog reguardless of the source of the light.
One cheap insurance method is to drape your darkcloth over the camera bellows and back before removing the darkslide, then expose like this and replace the darkslide before removing the darkcloth.