Re: DOF/Digitized Collecting

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Julius Martin writes:

>I have been reading with interest the discussions on DOF.  Don't get
>into the subject that technically myself.  Remember something about
>setting focus to a distance one third into the region you want to be in
>focus.  Will that be useful as a rule of thumb here.

That's the standard rule-of-thumb they teach flatty photographers (I
think it's sometimes called "zone focusing").  It's particularly useful
when you are taking action shots (e.g. sports events) and don't have
time to refocus on the subject each time, but you know the min. and max.
distance you need in focus (e.g. the width of the rink).

The "rule" in stereography is different; it says that the *entire* scene
must be in focus, front to back.  Using the rangefinder and hyperfocal
scale on your camera is one way to ensure this.  You find the distance
of the closest and furthest objects in the composition, and choose a
shutter speed and aperture such that these distances are within the
hyperfocal range.  Debate then ensued about whether the hyperfocal
tables on various cameras provide sufficient sharpness (i.e. a
sufficiently small "circle of confusion").

This is one of the things we're discussing: when can this rule be
successfully violated?  I think we're all in agreement that the answer
isn't "always", but at least some of us agree it also isn't "never".  So
now we're trying to define what works and why (at least, I am).

>Understand that Stan
>White has an up-coming article in Stereo World on what seems to be
>historical preservation of the present.  I feel strongly about that
>aspect of stereo photography.  Today is tomorrow's past and too many
>things of value and interest are disappearing everyday.  I'm continually
>reminded of the song wherein "they tore down paradise and put up a
>parking lot."

True.  Particularly annoying (to me at least) is the fact that many
interesting places (shopping malls, electronics stores, etc.) won't
allow photography for various reasons.  So when these places are
inevitably destroyed, there won't be *any* photographic record that
they ever existed!  (Think about how fascinating photos of storefronts
selling TVs and radios in the '40s and '50s are...  There won't be many
of these kinds of photos from the '90s, and probably none in stereo.)

	-Greg W.




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