Archived posting to the Leica Users Group, 2002/04/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]In a message dated 4/10/02 2:44:43 PM Eastern Daylight Time, mginex@panynj.gov writes: > Because I don't know any better, I guess. Just posed the question since I > have no experience with RF Leica's. > Sorry, Mike, I made an assumption I shouldn't have, that you did know about RF Leicas. M lenses have a cam whose curve activates a follower arm connected to a prism/mirror that determines the focus of the lens. The rangefinder base (the distance between the RF windows) determines the accuracy of the rangefinder - the wider the more accurate. That distance can be made more or less accurate by the magnification of the viewfinder itself. Leitz/Leica has found that 135mm lenses are the longest focal length that can be accurately focussed by M-cameras. In fact, in the 1960s, Leitz is believed to have made one or two prototypes of a 180mm f/2,8 Elmarit lens with "bugeyes" similar to those on the 135/2,8 Elmarit for M cameras. They found that this rig could not achieve adequate focussing accuracy. Leica lenses of 65mm and longer can be used with adapters on Leica reflex cameras; their focus is simply determined by the mirror, prism and focussing screen. Seth LaK 9 - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html