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Thread: JOBO I cannot get consistent results. WHY

  1. #1

    Join Date
    Mar 1999
    Posts
    11

    JOBO I cannot get consistent results. WHY

    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 she ets 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 test s.) Solution which I used in the drum is 400ml full strength D76 solution for the fi rst undiluted process and 200ml full strength D76 + 200ml water (400 ml total) f or 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 shee ts (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 depen ding 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

  2. #2

    JOBO I cannot get consistent results. WHY

    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

  3. #3

    Join Date
    Dec 1997
    Location
    Baraboo, Wisconsin
    Posts
    7,697

    JOBO I cannot get consistent results. WHY

    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
    Before you criticize someone, walk a mile in their shoes. That way when you do criticize them you'll be
    a mile away and you'll have their shoes.

  4. #4

    Join Date
    Feb 2000
    Location
    Reykjavík, Iceland
    Posts
    452

    JOBO I cannot get consistent results. WHY

    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.

  5. #5

    Join Date
    Nov 1999
    Location
    San Clemente, California
    Posts
    3,804

    JOBO I cannot get consistent results. WHY

    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.

  6. #6

    Join Date
    Nov 1998
    Posts
    93

    JOBO I cannot get consistent results. WHY

    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.

  7. #7

    Join Date
    Dec 1999
    Posts
    195

    JOBO I cannot get consistent results. WHY

    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

  8. #8

    Join Date
    Nov 1999
    Location
    San Clemente, California
    Posts
    3,804

    JOBO I cannot get consistent results. WHY

    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.

  9. #9

    Join Date
    Nov 1998
    Posts
    93

    JOBO I cannot get consistent results. WHY

    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.

  10. #10

    Join Date
    Oct 1998
    Posts
    106

    JOBO I cannot get consistent results. WHY

    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.

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