On May 3, 2005, at 3:12 PM, David Oswald wrote:
A 20-30mm lens would have to be a retrofocus design, wouldn't it? I'll be fascinated to see how Pentax manage that one. :-)
For us laypeople, what do you mean by a retrofocus design, and why do you say a 20 to 30mm lens would have to be that? Sorry to show my ignorance...
A retrofocus or inverted telephoto optical design allows the rear element of a lens to site further from the focus plane, allowing room for the mirror of an SLR. Most zoom lenses and most short focal length lenses for SLRs are retrofocus designs. A simplistic explanation with some graphics are here:
http://www.rondexter.com/library/retro_focus_and_tele.htm
Godfrey
