P3D Shutter speeds

[Keith Sanborn <mrzero@xxxxxxxxx>]

Dear Jason:

If you've already figured this one out, my apologies. You seem to already
know what's at stake. Anyway......

Your dilemma is a familiar one since I use a Bolex 16mm film camera which
as you might guess doesn't have standard shutter speeds. What I do with my
Minolta spot meter is to fudge things close by say using the closest
shutter speed I can find on the Minolta then changing the rating of the
film in the appropriate direction.

Example: My camera shutter speed is 1/85; my film is EI 100. I set the
meter to 1/120 (about 1/3 of a stop too fast) and rate the film at 120
(about 1/3 of a stop too high). So even though my shutter speed is too high
(implying I need a wider aperature) overrating the filmspeed implies I need
a correspondingly smaller aperature.

My example may not fit your situation because of the actual numbers
involved, but that way you can get a bit closer. This is usually close
enough, though I am usually shooting negative which has a lot more latitude
(rought plus or minus a stop) than the slide film (roughly plus or minus
1/2 stop) many stereo photographers use. Your mileage may vary depending on
the luminance range of your subject.

BTW: There is a rather rare French Stereo Camera which actually has
continuous shutter speed adjustment enabled by its unique air piston
shutter drive. The name of it escapes me at the moment.

Keith Sanborn



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