Archived posting to the Leica Users Group, 2003/04/24
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At 2:54 PM -0400 4/24/03, 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.
>
>Example:
>
>50mm, f2.8, 1M subject distance:
>
>COC of .033 gives a DOF of 0.07M
>COC of .06 gives a DOF of .128M
>
>Clearly, the COC highly modifies the DOF.
I meant that the usual application of COC is a lesser factor than the
focal length/aperture combination (actually, it's the aperture size
diameter that is the true determinant alone). I just overstated my
case to make the point.
The other, somewhat subjective component is: what do you expect from
the various formats in terms of 'sharpness'? If you expect nothing
more from a 4x5 shot blown up to 16x20 than from a 35mm shot blown up
to 16x20, then the COC becomes a much greater factor.
- --
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:henningw@archiphoto.com
|[ ]| http://www.archiphoto.com
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