Archived posting to the Leica Users Group, 1997/12/05
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 10:00 PM 12/4/97 -0800, you wrote: >I'm not a lens designer. I don't know anything about designing wide-angle >lenses, except for a few very simple ones. I'm not even a physicist. But Well, I'll defer to the optical experts who hang out with lens designers. They say that focal length does effect diffraction. There are lots of factors that are involved in diffraction in a lens system. One of them, according to the folks I've read from in the photographic press, is the angle of incidence of the light hitting the aperture. As for light knowing which angle it hits the aperture at, after studying a bit about quantum mechanics, I'm not so sure. :-) >A "diffraction-limited" optical system is one in which aberrations are so >small that the primary factor affecting image quality is the aperture >diffraction. Why do you say the numbers don't make sense? Have you Like I said, as far as I know, there are only two Leica lenses that fit that description. Both Apo Telyts. Like I said, I'll defer to the optical experts I've read. Like you, I don't design lenses. All I know is I've been told that stopping a wide angle lens down to F/22 will bring about more diffraction than a 180mm lens to f/22. But then, the physical aperture in the 19mm lens at that aperture is much smaller than the physical dimension (area of opening) in a 180 lens at the same aperture. Maybe the wave-pattern of the diffraction is influenced by that difference? ========== Eric Welch St. Joseph, MO http://www.ponyexpress.net/~ewelch Some people say that I'm superficial, but that's just on the surface.