Stephen Harrison (SH@stephenharrison.com)
Wed, 17 Mar 1999 23:26:58 -0800
I don't do pyro but I do dostraight D-76 for 5x7, 7x17 and 12x20 in a tube
roller made by Edwards Engineering. I use PVC opaque film tubes from Fred
Neumann at Darkroom innovations. My process of film development is BTZS
with each sheet being developed for different lenghts of time. My tube
roller will do #6 7x17 inch sheets in 3 inch diameter PVC tubes at 80 rpm
or# 3 sheets of 12x20 inch sheets of film at 60 rpm in 5 inch diameter
tubes or as many as 20 sheets of 5x7 sheet film at probably 120 rpm. I have
never had any streaking in the 5x7 sheets and the development is consistent
and even. I do however get slight streaking as Carl Weese wrote in the
highlights esp noticeable in 7x17 and more obvious in larger sheets of film
in overcast skies as he describes. All film is developed at 75 degrees
which is accurate and well controlled. The larger the sheet of film, the
more noticeable the streaking in the highlights. My service bureau told me
it was bromide drag which sounded reasonable. My tentative conclusion after
about 900 sheets of film is that the streaking is characteristic of rotary
tube developers in general and larger film formats in particular. Perhaps
if I could just spin the larger 5 inch tubes at 120 rpm, this would solve
the problem but it might take off. For now, with my larger sheets, I am
afraid I will have to tray develop at this point which is a pain given the
different processing times and the small size of my darkroom. There might
be a reprieve however as I just had a reversing circuit installed so that
the rotation reverses every 6 seconds similar to the Jobo. My guess is that
it will not help howeveron the 12x20 cheets. I will continue to rotary
develop the 7x17 inch sheets however as the streaking is unusual and so
slight and the efficiency of developing six sheets at a time so great.
Stephen Harrison
This archive was generated by hypermail 2.0b3 on Sat Nov 06 1999 - 10:09:03