Archived posting to the Leica Users Group, 2001/06/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]on 6/21/01 2:20 PM, Doug Herr at telyt@earthlink.net wrote: > Edd, > > Any lens' performance degrades at small apertures because of the greater > influence of diffraction as the light passes the aperture blades vs. the > normal image-forming light waves. I can't say from here whether the degree of > degradation in your lens is normal or not but in general don't use the > smallest apertures on ANY lens unless you have to. More precisely, if anyone cares, the effects of diffraction can at varioius apertures can be related to the size of the circle of confusion and the film format. - -- In 35mm, f/16 is the stop at which diffraction effects start to become visible (bigger than the standard allowable circle of confusion). - -- In 6x6, you have to stop down to f/32 before diffraction effects are significant. - -- In 4x5, diffraction effects become significant just beyond f/64 - -- in 8x10, you can stop down happily to f/128! The better the lens, the more you will notice the diffraction effects. I can certainly see them at f/16 and beyond on my Elmarit 28. - -- John Brownlow http://www.pinkheadedbug.com