Godfrey, your "Geekdom" is impressive and appears unlimited. :)) Thanks, again, for your time and consideration in dealing with my out-dated ideas.
Jack --- Godfrey DiGiorgi <[EMAIL PROTECTED]> wrote: > The prime reason for the use of aspheric glass surfaces has to do > with simplifying and reducing costs in manufacture where using > multiple spherical section elements would either more costly or > produce lower quality, given today's manufacturing processes. Same > reason as using ED glasses. > > Projection onto a flat sensor or film surface has been an embedded > assumption in the design of camera lenses for many many years, with > few exceptions. > > Some history on the exception that I know of: > The Minox ultraminiature cameras obtained an extra measure of > resolution and quality by incorporating a matched-curvature pressure > > plate which clamped the film into position when the shutter was > cocked, until such time as lens design, materials and manufacture > made it unnecessary. The original Complan lens introduced in the late > > 1940s had a five element design, the rear element was in contact with > > the film to enforce the curvature but problems with scratching and > tolerances were such that a revised, four element design replaced it > > with the introduction of the Minox III in 1951, and the revised four > > element Complan was retrofitted to the majority of the Minox II > cameras as well. Around 1973, the Complan lens was replaced by the > Minox lens in the Minox C model run, which was designed for a flat > pressure plate/film plane. > > It's much more expensive and much more difficult to manufacture a > sensor/film gate with a matched curvature, particularly if you are > talking about an interchangeable lens system camera. > > Godfrey > > On Oct 20, 2006, at 11:34 AM, Jack Davis wrote: > > > That's the prime reason for aspheric glass? > > > > Jack > > > > --- John Francis <[EMAIL PROTECTED]> wrote: > > > >> On Fri, Oct 20, 2006 at 10:32:46AM -0700, Jack Davis wrote: > >>> Would it make sense to develop a concave sensor? Finest possible > >> focus > >>> would then be possible due to a constant light path distance > across > >> the > >>> sensor. > >>> Varying focal lengths a problem? Somewhat accommodated by a > sensor > >> that > >>> moves in and out? > >>> > >>> Jack > >> > >> It only makes sense if you don't expect to use it with any lenses > >> currently in use, all of which are designed for a flat sensor. > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
