JOBO Processing Questiongreenspun.com : LUSENET : Large format photography : One Thread
I have a JOBO CPP2 rotary processor with a 5 sheet 3005 drum and shoot 8 x 10 and 5 x 7 sheet film. My film is T Max 100 (5 x 7) and I use TMax RS developer. I also use Tri X (8 x 10) with D 76 developer. JOBO lists various chemical volumes to handle anywhere from one to 5 sheets, depending upon the format.
Has anyone used less than a full 5 sheet run, such as one or two sheets at the volumes listed and did you have consistent results compared to processing a full five sheets ? I read once where a photographer recommended that when processing less than the full five sheets you should fill the remaining slots with unexposed film to exhaust the developer. Using less than the full five sheets was not recommended. Seems like a waste of film and chemistry to me, but I wanted to check with others experience on this subject.
Thanks in advance.
-- Michael Kadillak (firstname.lastname@example.org), November 28, 1998
I routinely process 35mm, 120 and 4x5 film and have never bothered making sure my tanks are full of film. I use a CPE-2 Plus and whatever amount of chemistry the tanks need. The film comes out consistent whether the reels are full or if I just have two sheets (or one roll) in the tank. The only developer I'm aware of that varies with the amount of film in the tank is Kodak X-TOL, and Kodak provides instructions for processing times with different amounts of film. If you are really worried about this you can run shoot some test negatives and get densitometer readins, but I doubt you'll find more than standard deviation from one processing run to the next.
-- Darron Spohn (email@example.com), December 01, 1998.
I shoot 4x5 TMax100 and process it in 3006 drums in a CPP2 Jobo and have gotten very consistent results by filling empty chambers with old film exposed to room light. 1 sheet of room light exposed film equals 2 sheets of normally exposed film, and 1/2 sheet equals 1 normally exposed sheet. This method keeps the volume of developer to exposed silver ratio consistent which is important with TMax films. This also allows me to keep the amount of chemistry the same in all of my procesing runs. Hope this helps.
-- Rob Karosis (firstname.lastname@example.org), December 02, 1998.
With 3010 drum for 4x5 T-MAX 100 and with 3005 drum for 8x10 T-MAX 400 both developed with T-MAX RS, I have never had problem without inserting films into empty slots. I use maximum amount of developer when full loaded films are developed. When I process, for example, just 2 sheets with 3005, I reduce about 50% of developer. I have not done "lab-test" with a densitometer(I don't have), but I think there's no difference.
-- Shigehiro Ishii (email@example.com), December 03, 1998.
I have the CPP2 with the 3010 drum and have never processed 10 4x5 sheets before nor have I filled the empty slots with any film. I process both color film (using C-41 chemistry) and TMAX b&w (using TMax RS developer) without any problems. I use the volumes as recommended by JOBO for the amount of film I process.
I have stopped doing b&w for about a year now so my memory is a little vague. However, here is something to consider. If you process TMax RS chemistry at the recommended agitation speeds you will get a variation of +/- 0.09 density units over a 4x5 negative when exposed to a uniformly lighted gray card and a Zone I placement. This means that there could be a 1/2 stop difference (0.18 density units) from one side of the negative to the other do to agitation irregularities. This may even be worse for a 8x10. As you move up the scale and apply a higher Zone placement this variation bcomes even more pronounced. I believe I was seeing 1.5 stop variations (+/- 0.22) at Zone VI. If you reduce your agitation speed to one notch below "F" on the motor nob (real real slow) you can reduce that variation to +/- 0.03 for a Zone I placement which is a significant improvement. The remaining processing steps can be done at "4". Of course your development times will change (I think), but the results are worth the effort to recalibrate your system. To fine tune your system to this level, it is imparative that the light falling on your gray card is absolutely uniform. This is very difficult to do, but it can be done.
-- Stephen Willard (firstname.lastname@example.org), December 03, 1998.