The other advantage of a step-up ring is that it makes it easier to ensure that no visible light gets through, because the size of the bits of film is much larger than the size of the hole that the lens needs. A third advantage is that the step-up ring is threaded to take a 37mm (or whatever) second thing, so I just tucked the circles of film into the screw threads and they stay in place nicely, no glue needed and I can take them out if required. |