Archived posting to the Leica Users Group, 1997/12/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]My understanding was that retro-focus lenses were the result of the SLR- the rear element of really wide lenses interfered with the mirror; since the element is further away from the film, the angle of which the COS affects is smaller. Were or are there any retrofocus LTM or M lenses, and if so was the design used to eliminate any fall off on the edges of the field? >In optics these are part of the 'cos to the fourth' function that standard >construction lenses obey in a general way. With a bit of fudging this can >be compensated for to a small degree. If you want a lot better eveness of >illumination, retrofocus lenses are the ticket. You get a lot of other >problems, but eveness of illumination can be greatly improved. > >Telephoto designs make matters worse, by causing more falloff than the >'cos-fourth' law dictates, but it usually doesn't matter much because >telephoto designs are used on long focal lengths, where the 'cos-fourth' >falloff is small anyways. > > > * Henning J. Wulff > /|\ Wulff Photography & Design > /###\ mailto:henningw@archiphoto.com > |[ ]| http://www.archiphoto.com > >