Re: [Leica] depth of field..depth of focus?

[InfinityDT@aol.com]

In a message dated 9/11/99 1:09:15 PM Eastern Daylight Time, 
tedgrant@islandnet.com writes:

<< I had a young photo student ask me, "Why do they call it depth of field
 when it's really a kind of "depth of focus?" >>

This is how I always heard it: Depth of field is the area from near to far in 
the scene where points in the scene will be represented by circles of 
confusion of a specified diameter on the slide or negative, sometimes 
referred to as the "zone of acceptible sharpness".  Depth of *focus* is the 
*extremely* shallow zone fore and aft of the film plane within which a point 
focused *at* the film plane will be rendered acceptibly sharp, i.e. the +/- 
tolerance for misalignment of the lens-body-film relation.