Archived posting to the Leica Users Group, 2004/02/20

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Subject: Re: [Leica] Digital DOF
From: "Jacques Bilinski & Barbara Bradbury" <jbilin@axionet.com>
Date: Fri, 20 Feb 2004 13:14:35 -0800
References: <000201c3f75c$658235b0$6401a8c0@dorysrusp4> <p05100300bc5b695f858c@[10.0.1.5]> <002301c3f7db$8d202b20$6501a8c0@jbilinsk> <p05100302bc5c121f430d@[10.0.1.5]>

> In practice that is true; you get greater 'effective' depth of field
> with a small-sensor digicam than with a 35mm camera used at the same
> aperture, but not nearly as great a depth of field as the very short
> focal lengths and medium apertures would lead you to believe from
> film experience.
>
Thanks. I think I've finally sorted all this stuff out in my mind. When you
take a photo the reason that only one plane is in focus is because the light
from the subject enters the camera not at a single point but rather a
circular disk (the front of the lens). It is the diameter of this disk that
will determine how fuzzy the background will be in the final print. The size
of the negative or sensor and the magnification when enlarging don't matter
as long as the end result is the same size. The same diameter disk
(effective diameter of lens) represents a wider F stop (smaller f number) if
the film or sensor size is larger.

The term "aperature" in photography is often used synonymously with "f stop"
but in astronomy a wide aperature telescope refers to a telescope with a
large diameter lens rather than the focal ratio. So this can lead to
confusion.

PS Sorry Ted. I promise I'll stop now.





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In reply to: Message from "Don Dory" <dorysrus@mindspring.com> (RE: [Leica] Digital DOF)
Message from Henning Wulff <henningw@archiphoto.com> (RE: [Leica] Digital DOF)
Message from "Jacques Bilinski & Barbara Bradbury" <jbilin@axionet.com> (Re: [Leica] Digital DOF)
Message from Henning Wulff <henningw@archiphoto.com> (Re: [Leica] Digital DOF)