I need to use partial diopter lenses in a project. These would be ones with powers of +0.25, +0.50, and +0.75, rather than the usual photographic close-up powers of +1, +2, and +3 with which many of us are already familiar. As well, I need them to have a diameter of 24 or 25 millimeters. I have done some looking via the internet and a couple of opticians, but have only been able to locate them with diameters of 37 or 42mm. If anyone has some suggestions or ideas, I would be grateful for their assistance. Nathan Prichard
