Archived posting to the Leica Users Group, 2009/09/24

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Subject: [Leica] Circle of Confusion (was: Re: Obscura 4x5 Piccolino)
From: wildlightphoto at earthlink.net (wildlightphoto at earthlink.net)
Date: Thu, 24 Sep 2009 11:32:55 -0400

leo wesson wrote:

>>>
maybe, it's confusing!  it's what we called it in school.....
http://en.wikipedia.org/wiki/Circle_of_confusion

Leo Wesson
Photographer/Videographer
817.733.9157
www.leowesson.com


On Thu, Sep 24, 2009 at 6:00 AM, wildlightphoto at earthlink.net <
wildlightphoto at earthlink.net> wrote:

> leo wesson wrote:
>
> >>>
> amount of lens movements required is the deciding factor on what type of
> lens to buy.  larger circle of confusion=more movements
> (tilt/shift/rise/fall)
> <<<
>
> Wouldn't that be "image circle", not "circle of confusion"?
>

The Circle of Confusion (CoC) is the image on the film plane of a point of
light on the subject.  Ideally, neglecting diffraction effects, the CoC for
a correctly focussed point on the subject is also a point on the image
plane.  The CoC is bigger/less pointy when focus is off or when the lens
has has more abberations.  The image circle is the size of the image the
lens can make at the film/sensor plane.  Most lenses for 24mm x 36mm
cameras have an image circle that covers the 24mm x 36mm area, and little
or no more.  A bigger image circle allows more shift and/or tilt.

Doug Herr
Birdman of Sacramento
http://www.wildlightphoto.com

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