Archived posting to the Leica Users Group, 1997/08/29
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Amilcar asked: <snip> >Several years ago I read that a camera's viewfinder is not a perfect zero diopter (due to the difference between the apparent distance of the focusing screen and other displays, I guess). I think generally it's a +1 diopter. Can you confirm this? A few block from were I live there's an optician that just fills your requirements, although I would like to see how he'll deal with a -7 diopter! <snip> You are correct that many SLR cameras have viewing screens that are projected out to about 1 meter. Most people, even adults needing reading glasses, can focus on the viewing screen with their distance prescription lenses. In some cases, camera reviews will indicate that the focusing screen and LEDs (for aperture and metering information) are not prjected out to the same distance. If the differences are small, its not a problem. Myopic lenses are always thicker at the edge and thinnest in the center. So a 10mm diameter corrective eye piece lens will still be rather thin. If it is made from a high index lens, with a refractive index of 1.55 or 1.60, it will be thinner. Even anti-reflective coatings can be applied to this lens prior to edging to decrease reflections. If this optician who offered to make a -7 diopter eye piece lens for you is a friend, hold onto him. He's going to work hard to make you happy. On the other hand, I'm sure he'd like to fill a prescription for spectacle lenses as well. I would prescribe 1 Day disposable lenses by Acuvue. Wear them to photograph for the day and then simply throw them out. Great idea since your prescripion can change over the years. Have a good weekend, Richard - ----------------------- Richard Clompus, OD West Chester, PA, USA