Archived posting to the Leica Users Group, 2004/02/19

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Subject: RE: [Leica] Digital DOF
From: Henning Wulff <henningw@archiphoto.com>
Date: Thu, 19 Feb 2004 23:38:36 -0800
References: <000201c3f75c$658235b0$6401a8c0@dorysrusp4>

At 9:51 PM -0500 2/19/04, Don Dory wrote:
>Jacques:
>It is not the sensor size that is determining the DOF.  It is the lens
>focal length.  On a small P&S digital you might have a 5-16mm focal
>length zoom roughly equivalent in image magnification to a 35-105 in
>35mm.  So if you were doing a portrait using the 16mm focal length on
>the P&S and a 100mm on the 35mm from the same position and aperture then
>you would indeed have very different DOF on any reasonable image size.
>Now, if I used a 16mm lens on my 35mm and cropped to the same image size
>then the DOF would be the same assuming the same aperture, distance to
>subject, and image size on finished image.
>
>Some of the confusion is coming from magnification factors with digital
>SLR's using different focal length lenses to put the same image on the
>ground glass.  Using the E-1 as an example, a 50mm lens magnifies like a
>100mm on a full frame digital or normal 35mm.  The 50mm retains the same
>DOF properties that it would have on 35mm so the DOF using the Olympus
>system at a given aperture and image magnification would be greater than
>the DOF that would happen with a 35mm system, 100mm lens, same aperture,
>and same image magnification.
>
>I hope that this helps.


I doubt it will. Sensor size, or rather the relationship between 
sensor size and the final image is indeed important in determining 
DOF.

Once again you are ignoring CoC considerations; ie, DOF on the 
negative is not the same as DOF on the print.

- -- 
    *            Henning J. Wulff
   /|\      Wulff Photography & Design
  /###\   mailto:henningw@archiphoto.com
  |[ ]|     http://www.archiphoto.com
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Replies: Reply from Dan C <leicaman@sympatico.ca> (Re: [Leica] Digital DOF)
Reply from "Jacques Bilinski & Barbara Bradbury" <jbilin@axionet.com> (Re: [Leica] Digital DOF)
In reply to: Message from "Don Dory" <dorysrus@mindspring.com> (RE: [Leica] Digital DOF)