T3D DOF uhsplained

[john bercovitz <bercov@xxxxxxxxxxx>]

If you're interested in DOF, could you go to 
http://www.angelfire.com/ca2/tech3d/images/
and pick up kdof.gif?  It's a picture of one 
of the cleverest ways of understanding DOF.
Note that relative aperture (f/number) doesn't
matter.  It's linear aperture (entrance pupil 
diameter, you can measure it) that matters.

If you this doesn't look intuitively obvious 
to you, I can give you a less elegant derivation, 
which I did, and which I am sure thousands have 
done before, but it's just plodding and it gives 
the same answer.

John B


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