Archived posting to the Leica Users Group, 1999/11/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>>The real reason that all SLR's cut off some of the frame is to enable them to >>make the mirror smaller - thus allowing a lighter, smaller mechanism. > >No, it's because it is very, very difficult to make a viewfinder that shows >exactly 100 percent of the frame. The mirrors on SLRs nowadays are plenty >big to convey the whole picture. The mirror is definitely not the issue. Mirrors have gotten longer while getting lighter with more sophisticated linkages to reduce bounce and image cut off. The problem is primarily associated with cost, weight and size. It's pretty easy to make a focusing screen of 24x36 dimension accurately, takes a bit of doing to align it perfectly but that's not so hard. The real problem comes when you try to make a quality pentaprism that will cover that big focusing screen. I've been told that the yield on 100% coverage pentaprisms is less than 30% ... most go back in the pot due to flaws. A prism which covers the screen properly is also large and heavy, requiring more bulk and support structure to keep it properly aligned. All that costs money along the way. Coverage became smaller and smaller as people wanted more compact cameras. Now the cameras are bigger than they've ever been, but it's due to the inclusion of conveniences like built in motor drives and handgrips. It surprises me that Leica does not put a 100% coverage finder in the R8, however. At the price and size of the camera, it surely shouldn't be too hard to do. Godfrey