In article <3u4qt2$gik@cello.hpl.hp.com>, jacobson@cello.hpl.hp.com
says...
>
>In article <3trkjo$iu6@newsstand.cit.cornell.edu>,
>Bob Neuman wrote:
>>wide-angles have more depth-of field,
>>BUT less depth-of-focus
>
>Well, actually, the depth of focus (max lens to film distance shift
>that can be tolerated) is just the max circle of confusion times the
>f-number. The focal length does not matter.
>
> -- David Jacobson

Ah, it appears that you are correct! I misdescribed an effect:
a touch of error in a lens mount focus scale and infinity stop is
far more critical in a very short lens for a format than the same
error in a much longer lens for the same format, i.e., a 20mm lens
for the 35mm format focused 2mm away from infinity will be correctly
focused at approximately one foot, whereas a 200mm lens moved 2mm
away from infinity focus will be correctly focused at something just
under 100 feet (from a quick observation of my lens focusing scales).
While the circles of confusion may be the same for a subject at
infinity, I can sure tell you which lens would be more useful for
picture taking if the error in spacing both lenses away from correct
infinity focus were the same 2mm! (A lot of photos can be taken with
a lens limited to a maximum of 80 feet, or so, but very few if the
lens is limited to 8 inches or thereabouts. Now you take the same
2mm error, and apply it to an 8mm lens.......) My point was that
allowable manufacturing tolerances for 35mm camera body depths and
lens infinity settings make things a bit iffy when the lens
focal-lengths get VERY short, resulting in a common occurance
of errors in lens distance markings and infinity stops with
super-wide-angle lenses. Hope this helps.