Archived posting to the Leica Users Group, 2001/05/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]There is what appears to be an incorrect statement in the bokeh explanation on the web page. Spherical aberration causes the off-axis rings of the lens to have a different focal length from each other. That is, a conceptual circular disk of the lens, with the axis at the center, will have a different focal length from a conceptual ring at the lens's outer periphery. Thus, if any spherical aberration is left uncorrected, the lens will not produce a point image from a point object. Herb (Ph.D. in physics in 1951, but "went wrong" and went into computer biz, so could be suffering from failing memory; however, I think my recollection of that part of optics is correct.) - -- Herbert Kanner kanner@acm.org 650-326-8204