[OM] CoC and DOF, was: The ones that get away.

[usher99]

Easy for Chuck to say as he has Dr. Focus at his beck and call.  Must 
repeat the olde saw that the real defintion of COC is a "group of 
photogs
standing in a circle discussing DOF".  I remember calculating the DOF 
by varying focal length--no significant change BUT..... the 
distribution of the DOF changes  as more of it is behind the focal 
point with a WA lens.  (from about 70% behind at 10mm to 52% at 100mm)  
I quit after a few minutes as my head hurt---less trouble with 
Schrödinger's wave  equation.

Mike



Just don't confuse Circle of Confusion with diffraction and the Airy
disk.  Both may be considered optical "spots" produced by a lens.  But
the Airy disk is a measure of the smallest spot a lens is capable of
producing at a given focal ratio... where the limitation is imposed by
diffraction.

The CoC is more a measure of the human eye's ability to resolve detail
See the illustration at top right of this page.
<http://en.wikipedia.org/wiki/Circle_of_confusion>
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