Archived posting to the Leica Users Group, 2003/04/24

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Subject: Re: [Leica] Digital Aesthetic
From: Johnny Deadman <lists@johnbrownlow.com>
Date: Thu, 24 Apr 2003 15:13:30 -0400

On Thursday, April 24, 2003, at 02:54 PM, Austin Franklin wrote:

> Henning,
>
>> DOF is dependent on focal length and aperture value
>> alone, and only slightly modified by the different circle of
>> confusion criteria for different formats.
>
> Good grief, Hemming.  The DOF is HIGHLY dependant on the COC.  The COC
> significantly modifies the DOF for the same focal length, aperture, and
> distance.

To be precise:

DOF = [sH/(H+s)] - [sH/(H-s)] = where H = f^2/Nc

H = hyperfocal distance
f = lens focal length
s = focus distance
N = f-number
c = circle of confusion

A quick expansion of the equation shows that for DOF varies roughly 
inversely with CoC.

- --
John Brownlow

http://www.pinkheadedbug.com
http://www.unintended-consequences.com

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