I'm building my first pinhole camera, using a small wooden cigar box that has a slightly recessed lid. The hole in the metal doesn't confuse me. But the size and shape of the hole in the box lid does. The lid of the box is recessed approximately 1/8" from the edge of the box (box is approximately 6" square). The actual thickness of the lid is another 1/8" or so. My thinking is that a hole of about 3/8", slightly countersunk, should allow for the most light to hit the actual plate that holds the pinhole. Am I making unnecessary work? Is there any guideline for this kind of thing? Thanks for your help.