T3D Re: DOF equal?

[john bercovitz <bercov@xxxxxxxxxxx>]

> But the 35mm advantage disappears if you englarge to EQUAL image 
> Magnifaction..e.g. the same f/stop has same depth of field at 
> equal magnification... 

I don't want to be contradictory but Dr. Kingslake says that if 
the camera has the same vantage point, and if the lenses have
the same linear aperture (not relative aperture aka f/stop), and 
the images produced have equal magnification, they will have the 
same DOF regardless of format.  In fact, that's what his diagram 
(which I have redrawn and which Tom has put at 
http://webman.mc.yu.edu/t3d/ ) 
shows.  Notice that the argument is made entirely in object space and 
has nothing to do with format size.  That's what makes his derivation 
so unique.  I have done the same thing in image space but it is not 
nearly as elegant.

I should also say that this derivation depends on your viewing the
photo correctly, that is from its center of perspective, which 
fortunately we do to a good approximation when we view stereo.

But perhaps I am just misunderstanding what you say.  If I do 
understand you, and you understand me, why not buy Kingslake's book 
and see if you disagree with his presentation?

Kingslake, Rudolf
Optics in Photography
SPIE Press, 1992
ISBN 0-8194-0763-1
Order from SPIE, PO Box 10, Bellingham, Washington 98227-0010
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PM06 Optics in Photography, R Kingslake, Author(s)
299 pages * Jun 1992 * $38 / $42 / $48 * Status: IN 

Hey!  While you're at it, pick up:

TT30 Optical Engineering Fundamentals, B H Walker, Author(s)
362 pages * Dec 1997 * $38 / $43 / $48 * Status: IN 

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Within North America, 5% of the total will be added.

John B


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