I am using the Jobo expert drums for 4x5 and 8x10 sheet film almost daily.
Not exactly the same thing but pretty close.
>Now I notice some peculiarities:
>For one thing, there's a dramatic difference between the test strip and
>the final, full-size sheet. In past, adding 10 to 15% to
>exposure and development seemed to compensate for the different way
>developer hits test strip and the large sheet.
Could this be developer activity levels, or is something else going on?
If it is the level of developer activity, then you can check this out quickly.
With the same developer, run a test strip, then an exposed big sheet, and
then a test strip. Compare all the densities. If the first test strip is
the same density as the last test strip and the big sheet is less dense then
it is something to do with the agitation differences. In that case just take
a previously developed sheet and tape your test strip to it. Having the big
sheet in the tube will ensure the agitation that you are looking for.
If the last test strip and the exposed sheet match in densities then it is
a developer activity/capacity thing.
>But I haven't gotten the hang of this for the tube, with, again, the
>problem more noticeable with lith than N31P. Taping test strip into the
>full-length tube near one end and carefully moving the tube across the
>tray and back is still unpleasantly off the mark. Any observations or
>advice on this (other than "use a whole sheet," which I already figured
>out) would be welcome.
Back when I printed color in a drum, taping test strips inside the drum never
worked well. If the test strips are long and skinny, there are two orientations
that you can tape them in. I always tried to have the test strip to cover the
circumference of the drum and often the tape would give up. I see no reason
why you couldn't tape the strip in the other orientation such that the long side
are closest to the ends of the tube. I finally started making square test
strips and had better success. This is may be helpful.
>And a stranger phenomenon: The lith film (which, granted, is goosey) will
>show development stripes, or more descriptively "rays," in the fully
>exposed margin along the length of the film (top and bottom of horizontal
>format). Not the short sides at the open ends of the tube, but the long
>sides stretching the interior length of the tube. It seems that developer
>cascades over the long edge, where sides of film don't quite meet in the
>circle, in ways to cause uneven development. The effects are rarely
>visible in image area, but still worrisome.
The cascading that you describe could well be causing this effect.
Try a slower agitation i.e. less cascading. Can you find a slightly smaller
tube
such that the film fits in all the way around such there is a minumum gap?
This too would ensure a less abrupt cascading. Also try adjusting the volume
of developer. Does this occur still occur with double the developer volume?
>A final question: I've bought some 16x20 inch N31P (Arkin, 212-686-8805,
>about $240 for box of 50), now need tube for 16x20, contemplate 16x20
>print drum for closed-tube development -- to avoid large open trays of
>chemical in small darkroom -- but have never used drum larger than Jobo
>4x5. Would the time it takes to pour developer out and stopbath in be a
>problem with very short development times (about 2 min for goosey lith, 3
>min for N31P)? Of course it would! Any other comments?
The Jobo expert drums for 4x5 and 8x10 are superb. I have not used the
print drums for larger films but I understand that Jobo has a film insert
for them and will make custom sized drums as well. You may want to develop your
lith at a lower temperature so that your development is closer to 3 or 4
minutes.
This should reduce, or eliminate, any "tiding" problems. A presoak may help too.
>And a footnote for folks contemplating tube development -- speed of
>rotation is a BIG variable.
Yes it is. The Jobo processors are wonderful since they are consistent in both
rotation and temperature (and no I don't work for Jobo). They are an excellent
investment since they take away a lot of the tedium of darkroom work. I bought
mine used and I am very happy with it.
Robert Hudyma, Email: rhudyma@idirect.com,
Semi-Tech Microelectronics, 131 McNabb Street, Markham Ontario Canada, L3R 5V7