Archived posting to the Leica Users Group, 1998/05/25
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 07:34 PM 5/25/98 -0700, Bryan Willman wrote: >The real point here is that Retrofocus lens is >physically longer than its focal length. So, >a 21mm for an M camera must be retrofocus, >since you can't fit the nodal point within 21mm >of the film plane. It's the other way around. A 21mm lens for an rf camera, such as the M, CAN be non-retrofocus, as you can design it readily so that the rear element is easily within 21mm of the shutter curtain/focal plane (yeah, yeah, there are two or three mm here, I realize!). But you cannot design such a lens for an SLR, and leave space for the mirror, which takes 35mm or so of depth. Reverse telephoto wide-angle designs were first made by Carl Zeiss immediately prior to World War II but were first popularized by Angenieux, who coined the trademark "Retrofocus" for such formulations. Marc msmall@roanoke.infi.net FAX: +540/343-7315 Cha robh bas fir gun ghras fir!