Archived posting to the Leica Users Group, 2007/10/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I just acquired ( from another Lugger) a 21mm F4 Voigtlander Skopar lens. What I notice is that this lens uses tiny elements. Whereas the Leica 21mm offerings, even though they are 1 stop faster, use much larger elements. Maybe 3 times the diameter. I thought that the F stop of the lens is dependent on the element size, and that the area of the element determined its speed. Going from F2.8 to F4 should be a doubling of the lens area... or around a 1.4 times the diameter of the lens. But t he actual lenses in question are substantially larger then this.... Is the 1 stop faster speed increasing the element size by this really large amount? What gives? Frank Filippone red735i@earthlink.net