Archived posting to the Leica Users Group, 2001/05/01

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] Re: Bokeh Explained
From: Herbert & Lee Kanner <kanner@acm.org>
Date: Tue, 1 May 2001 15:40:01 -0700
References: <200105010701.AAA10814@mejac.palo-alto.ca.us>

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