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Hi,
Somewhere I once read that, when using a tank to develop film, you should always make sure that the tank was full of film to capacity. That is, if your tank ho lds six sheets, but you only have four to develop, then you should add two unexp osed sheets to the tank.
If this is true, why?
Does it matter if you mix films (i.e. Tri-X and Tmax) when developing Tri-X? I can't see why it would.
Thanks, Robert
I regularly process 1 or 2 sheets of film in a Jobo expert tank. I rarely fill the tank to capacity with film. I have never had a problem with consistency, uneven development, or anything else.
I do not process different emulsions together primarily because the emulsions I use require different processing times.
-Bill
The second to last studio I worked with had three JOBO units, one for each process, and a 4th back-up. They would regularly shoot three shot tests and then process all three in the same drum to check exposure, etc.
For reason of consistency, you may wish to always have about the same amount of exposed film emulsion in the same amount of developer. For that purpose, one sheet of fully exposed film (out of the camera) equals two sheets of in-camera exposed film. (courtesy John Sexton workshop).
I have a small stack of outdated or wasted sheets at hand in the darkroom, to add to my developing tank if necessary.
If you use enough developer per sheet, you will not need to do this. I use 500ml of D-76 1:1 (or equivalent) per 8x10 sheet, in accordance to The Film Developing Cookbooks instructions. At this rate, I can only develop two sheets at a time.
I've had pretty bad experiences trying to use the Jobo tanks for 5x4 cut film. In fact Jobo contradict themselves in the instructions for the 2509 cut film adapter.The advertising blurb stated that you could fit 6 sheets into each adapter, and indeed there are six slots in the 2509. However, the instructions that come with the 2509 say that no more than 4 sheets should be developed in it at any one time.The problems I've experienced have been 'tide' marks and foaming marks. The foaming marks were obviously caused by air bubbles trapped between sheets of film that were too close together.
Note that the latest 4x5 reel from Jobo is the 2509n. The "n" model comes with plastic "panels" that snap onto the reel after the film is loaded to keep the sheets in place and improve agitation consistency. I recall Jobo admitting somewhere (check the Jobo Quarterly on the Jobo web sites) that the original 2509 had problems. I've seen no agitation problems at all with my 2509n. If you are having problems with the 2509, I'd recommend upgrading to the 2509n.
(Also, if you're looking for the 4x5 reels used, like on eBay, be sure that you know which you're getting.)