In some cameras, the ground glass comes with open corners. Supposedly, the adva ntage is the ability to look in through the back at the lens diaphragm as a chec k against vignetting. Questions about this:
1. What am I looking for? To see the entire diaphragm or just any part of it?
2. Will this help me to prevent dark corners and not just frank vignetting?
3. Presumably, one has to be stopped down for this to work accurately?
4. Any other tricks to check for vignetting? Frankly, I just don't see it on t he GG sometimes, even when checking carefully, and even when stopping down (inci dentally, why do I see vignetting _more clearly_ when I stop down? I thought th at increased the image circle?)
5. Is this enough questions for one post??