Re: trouble with BTZS software

----- Original Message -----
From: "shannon stoney" <sstoney@pdq.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, September 24, 2004 6:14 PM
Subject: trouble with BTZS software

> Hi,
>
> I did a film test last May and entered all the data into
> the plotter program, and then sent the curves to the Expo
> Dev softare, and everything seemed to be working fine. I
> exposed about fifty negatives or more this summer, and now
> I am back in Houston developing them. They seemed to be
> exposed perfectly, but they are way under-developed. The
> highlights are falling in the range of 0.9. Anybody have
> any idea how I messed up? I processed the film at 68
> degrees for the test and for the recent negatives. I used
> tubes. I used distilled water for test and negatives. I
> thought I was doing everything right!
>
> The times do seem a little screwed up. For example, for
> HP5+, for an SBR of 8.4, it says to develop for four
> minutes. That doesn't hardly seem long enough, but I
> followed directions, and sure enough, it's not long
> enough. Why did the software think my times should be so
> short? I checked the densitometer to make sure it was
> calibrated right.
>
> --shannon

   I don't know anything about this software or service. If
you have a densitometer its easy enough to calibrate your
development times. To do it right you also need a step wedge
but test exposures can be made in the camera.
   Generally, manufacturer's development data is pretty
accurate. Ilford offers on-line booklets with development
data for their films for several popular developers. Tubes
probably work with the constant agitation times for tray
development.
   Four minutes is too short anyway. Even with tray
development its hard to get uniform development with such
short times. I would dilute the developer and aim for around
8 minutes.
   What do you mean by SBR, this is not standard
nomenclature. Contrast is measured in three ways: gamma,
average gamma (called bar-G), and contrast index, the last
used mainly by Kodak. Bar-G and CI are ways of specifying
contrast of films with curved characteristics where gamma
may be different at different points on the characteristic
and therefore misleading.
   BTW, highlight density is not a good measure of contrast.
Density is mainly a matter of exposure. While increasing
development will also increase density it does so in
proportion to exposure, i.e., it increases the contrast. If
the shadow densities are low but present the problem is
underdevelopment. If the shadows are blank the film was
underexposed.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com