Archived posting to the Leica Users Group, 2000/11/27

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

Subject: Re: [Leica] bokeh analysis
From: Jean Marc Becker <jean-marc.becker@wanadoo.fr>
Date: Mon, 27 Nov 2000 22:36:12 +0100
References: <20001127032133.VXPV2410.femail6.sdc1.sfba.home.com@[65.1.114.25]>

> In light of the recent exchange over the "science" of out-of-focus  and
> bokeh, has anyone read the following from Harold Merlinger?
> 
> got to:
> http://fox.nstn.ca/~hmmerk/HMArtls.html#anchor26001
> 
> then download this file:
> ATVB.pdf
> 
> What about this?
> Interesting reading I think.
> 
> Henry Ambrose
> who when it comes to bokeh, calls it "moosh"

Very interesting thread especially for a european. It is a new notion
for me. 
Pictures I saw show a great analogy with the classical star test in
optical astronomy. Intra and extra focal images of a star show patterns
very similar  to these I saw in enlarged pictures of small brilliant
areas: a relatively dark area surrounded by a brilliant ring. The
patterns in enlarged pictures are clearly an envelop of some individual
diffraction figures. 
In astronomical optics, the symmetry between intra and extra focal
patterns is a very sensitive way to say if an optical element is well
corrected in regard of spherical aberration. 
A pinpoint star at focus, and a good symmetry between intra and extra
focal planes say that an optic is perfect. 
I think that bokeh could be exploited to achieve an actual optical test
for photographic objectives. 
Imagine a flat black plane with many steel brillant balls, like these of
roller bearings. A flash lightning the scene would produce a pretty fine
punctual source on each ball. Focusing in the middle of the plane would
produce many intra and extra focal patterns, and focused images would be
very thin. Probably a hard test for many optics...

JMB

In reply to: Message from Henry Ambrose <digphoto@telalink.net> (Re: [Leica] bokeh analysis)