JOBO I cannot get consistent results. WHY : LUSENET : Large format photography : One Thread

Hi, I've posted some questions about developing T-Max film recently and I've been running film test with JOBO, but I cannot get consistent results. Maybe the way I'm doing is wrong. Please help!! First of all, I've been testing D-76 developer with T-Max 100/400 8x10 film. last couple of days. I use JOBO CPA-2 processor with 3005 drum which holds 5 sheets of 8x10. The problem is that density differs depending on number of film in drum. I got good zone 8 density for 7 1/2min at 70F (straight) and 12min at 70F (1:1) with two sheets in the drum. (Those films were 3 stop over-exposed for this tests.) Solution which I used in the drum is 400ml full strength D76 solution for the first undiluted process and 200ml full strength D76 + 200ml water (400 ml total) for the second diluted process. I believe that's enough to develop two sheets of 8x10. However, when I process 3 sheets (600ml total), 4sheets (800ml total), or 5 sheets (1000ml total), negative always came out dense at same time and tempature. It shows that those developing times work only when I have two sheets in drum!! Wired. I thought this is the way I have to do, adjusting the quantity of solution depending on number of film in drum. Maybe not? Should I always use1000ml solution in drum in spite of number of films in order to achieve consistent results? Am I using too much chemicals? Same thing happened with Xtol test. Any input will be appreciated! Thanks in advance. riichi

-- riichi (, December 27, 2001


Hi, I wouldn't use anything but Tmax Developer on Tmax films if I were you. I have had nothing but trouble when I try experiments. Set up a standard run with a standard number of sheets to develop and stick with it. If you add or subtract it will change the times needed for specific results. I use a unicolor drum and have had really good, consistant results. You should be able to do the same with the Jobo. Good luck. Doug

-- Doug Theall (, December 27, 2001.

I don't normally use a Jobo system but I did attend a two week workshop where it was used. The instructor (John Sexton) recommended using T Max RS developer, diluted 1-9. As I recall(it's been a few years so please don't take any of this as gospel), we also were told to put one sheet of waste film in the drum to make up for every two empty slots (we were using a drum that held something like 10 sheets of 4x5 film). For example, if we were processing 4 sheets of film, we would add three sheets of waste film to have the equivalent of 10 sheets in the drum. I think the waste film was just some sheets that had already been processed that we used over and over (i.e. I don't think we used new, unexposed film each time). I don't remember whether we used the same amount of devleoper every time or whether it was adjusted depending on the number of sheets of film to be processed. If someone here doesn't give you definitive answers, I'd suggest calling Jobo with your questions.

-- Brian Ellis (, December 28, 2001.

JOBO says 270 cc minimum for the 3005 drum. For 1 or 2 sheets that is sufficent. For 3 sheets you need 380 cc, for 4 sheets you need 510 cc and 630 for 5 sheets. Those quantities are enough if the developer is not too diluted. Maybee you use a too slow a rotation speed. Jobo says 50 cycles a minute.

-- Gudmundur Ingˇlfsson (, December 28, 2001.

Anchell & Troop contend that you need 250ml of a developer's "stock" solution for each 80 square inch of film developed. If one accepts that, you should be able to do four 8x10 sheets in 1000 ml of undiluted D-76 in you Jobo, or two sheets if you use 1000 ml of D-76 diluted 1:1. I've been taking this approach and have never seen any variation in results, but my shooting volume is very low, so processing only two sheets at a time is not a problem for me.

Various schemes exist for getting more sheets out of a given quantity of developer, some described above. A potential problem with them is that we don't usually shoot subjects with identical average density on each sheet. This means that, relying on partially exhausting developer and establishing a development time to compensate, differences in subjects will likely lead to variations from one processing run to the next. You will need to establish how much variability you can accept. The less developer you use and the more sheet-to-sheet average exposure difference, the more your process results will vary.

-- Sal Santamaura (, December 28, 2001.

I recall John Sexton advising that you should always use full batches of film. But what if you don't have a full batch of film to develop? A completely exposed sheet of film is equal to 2 normally exposed sheets so a half of a sheet of film to one normally exposed sheet. My tests were going all over the place until I started always using full batches.

-- Jeff White (, December 28, 2001.

Sextone uses a 3010 which allows for processing 10 sheets of film. According to the handout he provides, he uses 850-900ml of mixed developer. 10 4x5 sheets equal 200 spquare inches. Two 8x10 equal 160 sg. inches.

I would try increasing the quantity of developer. And yes Sexton does recommend processing full batches of film. As a practical matter, i have processed less than ten with 850-900ml developer and produced fine negatives. But I hardly ever use less than that amount of developer. So i would retest using much more developer and see what happens. Bob

-- Bob Moulton (, December 28, 2001.

T-Max RS basic dilution is 1:4. The 250 ml guideline applies to this "full strength" mixture. Therefore, if Sexton dilutes 1:9, 500 ml would be needed per 80 square inches. Since 10 4x5 sheets in the 3010 drum amount to 200 square inches of emulsion, 2.5 x 500 ml = 1,250 ml of 1:9 T-Max RS is necessary for "carefree" processing. Only the Autolabs can rotate that much solution, and I haven't even checked whether the 3010 will accept it. Sexton has most likely come up with his approach as a means to stabilize results with sub-optimal developer quantity. "Waste film" used when less than ten sheets are developed cannot be previously processed, or it would fail to provide the controlled exhaustion desired.

-- Sal Santamaura (, December 28, 2001.

I am not sure what Sal means by "carefree" processing and I am sure the numbers that he is quoting must come from some Kodak information but those numbers are very conservative. I use the BTZS tubes and T- Max RS at 1:9 which equates to 6ml of concentrate for a sheet of 4x5 film and my tests haven't budged an inch in 6 years. If you would like to see my Test Data then click on this link. Riichi I would suggest that you go to JOBOs site and there they have a newsletter written by John Sexton. It has all of the information that you are needing.

-- Jeff White (, December 29, 2001.

I use D76 with TMX 1:1 on (4X5 in 3006 drum) and have no problems with consistency. I use the solution quanitity recommended by Sal of 250ml stock per 80 sq in film. I have never run with less than a full drum of film. I think your problem may be partly the quantity of developer you used (esp when used 1:1). D76 is a good choice for these films. Don't use it if it has been mixed for more than 2-3 months though as developer activity increases with age.

-- Gary Frost (, December 29, 2001.

The 250 ml per 80 square inch figure is not from Kodak information; it's an Anchell & Troop recommendation. I applied the word "carefree" to indicate that, if one uses this admittedly conservative developer-to-film ratio, exhaustion will not occur regardless of how fully or minimally exposed any or all sheets are. One time fits all, without need for 'extra' sheets of film to work around exhaustion.

-- Sal Santamaura (, December 29, 2001.

Hi Riichi, I use an ALT2500 in work, with the 3005 drum and the 3010 drums, On Tmax film I only use HC110 1-9 dilution, have the machine set to 210ml per drum, this is sufficent for my needs, and I obly run FULL drums, the program is automatic, I think I increased the developer slightly, and the clearing agent slightly to get these results. Next week in work I'll check my notes and let u know the change from the set program. for the E-6, and the C-41, I still use the 210 ml per run, of chemicals, and still only run full drums. Bill

-- Bill Jefferson (, December 29, 2001.

Moderation questions? read the FAQ