Archived posting to the Leica Users Group, 1999/12/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 10:35 AM -0800 12/1/99, Ken Iisaka wrote: >From: Mike Johnston <michaeljohnston@ameritech.net> >> >>>>> >> At 07:12 PM 11/30/1999 -0800, Ken Iisaka wrote: >> >I concur. I have been told that Nikon designers were tempted to change >the >> >mount to remedy its deficiencies, namely the long distance between the >> >flange and the film plane, and the diameter of the mount >> >> Whoever they were are wrong. I have it from the head of NPS that this is >> not the case. >> >> Eric Welch >> Carlsbad, CA >> >> Eric, >> I don't think this is correct--I think Ken is right. Several lens >> designers have told me that the diameter of the exit pupil is the third >> biggest limitation on the design of fast lenses for SLRs--first if you >> discount selling price and size, which are the two limiting factors that >> usually beat it out. Have you ever seen a Canon 50mm f/1? It obviously >> uses every millimeter of the exit pupil. > >and if you see the rear element of a Nikon 50/1.2, 55/1.2 and 58/1.2, every >millimeter of space is used. As the mater of fact, the rear element is >trimmed a little bit for one of the tabs. These rear elements are as far >back as they can be placed without interference with the mirror, and there >is no physical way to implement a larger exit pupil that determines the >f-stop. > >The anecdote about the decision comes from a friend who is in the camera >design group at Nikon who shall remain nameless to protect his job security. There definitely are design constraints placed on someone who has only a smaller diameter mount to work with, but it's the _entrance_ pupil that determines the f-stop, not the _exit_ pupil. The size of the Nikon's mount does not preclude a 50/1, it just makes it slightly more difficult. * Henning J. Wulff /|\ Wulff Photography & Design /###\ mailto:henningw@archiphoto.com |[ ]| http://www.archiphoto.com