A note on measuring your pinhole diameter - you can scan the image at a high resolution (2000 dpi or so) enlarge the hell out of it and then use a graphics editor - Adobe etc, (GIMP is free) to determine the number of pixels the hole is. Based on your scan resolution you can determine what the per pixel width is and, in turn, the actual pinhole diameter. I've checked my holes with a microscope and and its proved to be a pretty darn accurate method.