The Jobo system comes in two varieties, tanks for film, and drums for
prints. I think it's only the print drums that are meant to be
agitated by spinning, the tanks are more suited to inversion
agitation. I've got a load of info on the Jobo system stashed away
somewhere, I'll look it out if I can find it.
I bought a Jobo system specifically for 5"x4" processing and was
really disappointed with the results. Apart from the fiddly loading,
it gave uneven development and foaming marks if all the film-slots
were filled. I now use a small sealable stainless-steel deep tank with
individual film holders.
-- Pete Andrews (p.l.andrews@bham.ac.uk), March 14, 2000.
I have no experience with the tank you are using but I use Jobo all
the time both with tanks for roll film and expert drums for large
format. The expert drums are highly recommended for sheets,
surpassing quality of the 4x5 reel/tank system by far. But your tank
can very easily be rolls in a tub, contrary to the first post. Rotary
processing is an extremely even, accurate way of processing but
frought with procedural problems like with any method. Once you get
your hand rotation down it should work beautifully. I have an ATL 2
and it contributes speed, evenness, accuracy and chemical tempering,
but not much else if your hand rotation skill are honed. For me there
isn't a better way to process. I use BTZS tubes for really big stuff
and on the road, but always come home to my Jobo happily.
As for amounts, the other posts were right on and I can't add to it.
For sheet film, if you can gauge it somehow, rotation is best at about
75rpm. Roll film, in Jobo, is done at a higher rate...100 rpm.
-- Rob Tucher (rtphotodoc@juno.com), March 17, 2000.
I use the Jobo system with inversion agitation for B&W work. Rotary
processing isn't particularly recommended for B&W because of
potential streaking. A lot of things, such as developer, can
influence wheter or not rotary works well with B& W, so I just avoid
the problem by not using rotaty processing.
With inversion agitation, I never get any streaking. I load only the
bottom reel, and use the top to keep the lower one down. (I'm going
to cut a piece of plastic pipe to do this when I get around to it.)
An article in one of the good darkroom magazines, a few years back,
indicated the success of using stainless tanks for roll film, with
twice as much tank height as the film took up, and just enough
developer to cover the reels. During inversion, all the developer
moves to the top, allowing full intermixing of depleted and fresh
developer, and full flow past the reels and film edges. My approach
with the Jobo duplicates this effect. I've never had any agitation
problems as a result.
I measured 1.4 liters as the minimum to completely cover the lower
reel, so that is what I use. Since this is a lot of liquid I've tried
two approaches: very dilute developer one-shot developers and reusing
full strength developers. The second approach really requires
replenishment or adjusting times for the number of films previously
processed. The first approach is easier and more likely to give
consistent results, so I recommend it. Try Xtol at 1:3. Kodak
publishes times for this dilution. You could use other highly diluted
developers but you'll have to test for the proper time.
If you try the rotary process:
1. Make sure you use enough developer concentrate for the film area
you are processing. You can breakdown the capacity. For example, if
it says 1 quart will process 10 8x10 sheets. for 6 sheets of 4x5 you
need 32 ounces divided by 10 (to get ounces per 8x10 sheet)
multiplied 1.5 (6 sheets of 4x5 = 1.5 sheets of 8x10) or 4.8 ounces
of the stock as a minimum. You need to do this calculation as well if
you are doing inversion processing.
2. Make sure the developer (straight or diluted) covers the film when
the tank is horizontal. This is probably the volume indicated on the
tank, and it doesn't matter if you use one or 2 reels, since the
volume of the film itself is inconsequential. You're just trying to
cover all the film with the developer puddle.
Best of luck,
Charlie
-- Charlie Strack (charlie_strack@sti.com), March 21, 2000.