Carl Weese (cjweese@wtco.net)
Wed, 20 Jan 1999 11:05:31 -0500
Could you modify your header to tell us your name--Nash Computer is a
little impersonal...
My understanding is that the blue channel of a tri-color densitometer
can be used to calibrate pyro negatives, but frankly I'd say it's a
waste of time.
Also, your tests in 1/3 stop increments are much too picky: they're what
David Vestal calls "pussyfooting". To get some real information, test at
ei 800, 400, 200, 100, 50, and 25. What you'll find is that the last
three all print well, though the 25 may take a year or so to expose the
print <s>.
Find yourself a white building with a nice deep porch that casts a heavy
shadow in full sunlight. Your TXT exposure will be 1/4 sec at f/45.
Bracket exposures a couple stops each way (with the aperture, not the
shutter--that's much more likely to be accurate) and develop for seven
minutes in Rollo on your Jobo in an expert drum. Make prints. If they're
too flat, run the test again and develop for ten minutes. If they're too
contrasty, repeat and develop for five minutes.
My practice is to shoot TXT at 1/4 sec @f/45 for a subject in sunlight
with significant shadows. If the shadows are really important I'll go to
1/2 second. If there are no important shadows at all I'll move up to
1/8. If the subject is not in sunlight I meter the deepest areas in
which I want full detail with a calibrated Minolta Spotmeter F set to ei
200, mentally "place" those values on Zone III and then meter something
bright in the image. If it is at least as high as Zone VIII, that's the
exposure. If it isn't, I use an exposure high enough to get the bright
stuff on VIII. If the proper placement of the shadow value puts a high
value on Zone IX or X, that's fine. If it's getting up into XII or XIII
I might actually note the holder number and give that negative reduced
development.
These negatives will also print well on some variable contrast silver
papers with no filtration. Interestingly, a well-exposed negative of a
low contrast subject prints nicely, and a well-exposed (for the shadows)
negative of a high contrast subject will also print well without any
contrast modification (VC filters) but may require as much as 2 stops
more exposure. This appears to fly in the face of all Zone and BTZS
theory, which rather delights me.
---Carl
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