----- Original Message ----- From: "J. C. O'Connell"
Subject: RE: M42 ultra-wide
thanks for sending the info on the lenses you mentioned. Time for a pop quiz.
Anybody know why a 14mm DA lens with 90 degrees coverage would be bigger, slower, and costlier to make than the 20 mm lens with 94 degress coverage ASSUMING identical image quality?
I am pretty sure I know why. The reason seems obvious to me but what do you all think the reason is?????
The placement of the rear nodal point outside the lens has a lot to do with it.
Removing the mirror assembly would allow the lens designers a lot of freedom to make smaller lenses, at the expense of TTL viewfinders.
William Robb
