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  1. #1

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    Jobo Drum Speed?

    I just purchased a near new CPA-2 processor and have a few questions regarding drum speed for film processing. I mainly will be using it with the expert 4x5/5x7 and 5x7/8x10 drums. I previously have used them on a uniroller and had very good results but have cut my processing time dramatically to keep contrast down. I didn't receive any information with the Jobo but understand the F setting is for film. Last evening I did a run of 4x5 as a test and found contrast to be quite high using the times from the uniroller days. Now I need to reduce time from the 6 minutes I generally find good for normal processing and am concerned it will run less than 5 minutes. For consistency I do not want to get below 5 minutes. Now the question, I can adjust the speed of the rotation to a slower speed than the F setting but want to know if this will put an excessive load on the motor. I believe that going to the lowest speed will reduce the need to cut process times below 5 minutes. I will also say that I'm running most of my film with 1:47 Ilford HC and don't think I should dilute any more due to sq in area vs chemical volume vs oxidation of the developer. Any experience with this?

    Thanks!

  2. #2
    TheFlyingCamera's Avatar
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    I've had no problems running my CPA 2 at the very slowest possible speed - basically, I turn dial just past where it clicks "on" and let it go. Can't speak to your developer issue as I've never used Ilford HC.

  3. #3
    Jim Noel's Avatar
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    I use the same method with Expert drums - Turn o njust until it clicks and the drum begins turning. Works great with all of the several developers iuse.
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

  4. #4

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    Just out of curiosity what film / Dev. combo do you use? How much time did you have to shave off non rotary times? With the unicolor method I wound up using 1:47 HC/HC110 and used reduced times from 1:32 dilutions. I think I wound up shaving off about a minute to a minute and a half for HP-5 and FP-4.

    Are you using the slow speed for roll film too?

  5. #5

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    Going for a slower speed has more to do with consistency and saving the developer from oxidizing too fast. The slower speed will also save the motor. (A higher speed will put more strain to the motor because of the rather high intertia with the large Expert drums.) As I do most of my processing in Pyro and Pyrocat developers, oxidizing is an issue for me.
    Now, developing times will change if you go slower/faster, but not that much. I.e. you cannot solve the problem you have (i.e. "5 minutes") by just setting the speed a bit slower. The main thing is to be consistent with the speed setting.
    Anyhow, the consensus in many threads here and on lfphoto.info is to use the slowest speed possible.
    You are correct about not going below 5 minutes, but if you have to you have to. Now, are you processing at 20 deg C (isn't that 68deg F ?), else you can go down to that temperature and get longer times. (If that is possible in your darkroom. I know that many areas in the US have problems with water being warmer than 75 deg in the summertime.)
    Also, are you using a prewet before developing the film? First, using a prewet will add some 20sec to the developing time (as compared to not using a prewet). Second, if you still have to go for a shorter time than 5 minutes, a prewetted film will develop more consistent. Last, Jobo recommends to always use a 5 minute prewet with most processes (except E6 and C41).

    To answer your last question, as I'm using the 2500 series drums for rollfilm, I know that I can yank the speed up a little bit. I normally use the F setting for rollfilm. (But I turn the speed up a bit when I wash the film.)

    //Björn

  6. #6

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    I'm doing a 2 minute prewet. I'm guessing the 5 minute recommendation is more a function of getting the drum to temp rather than saturate the emulsion. By dropping the speed to the lowest point I now have a very nice neg with 5-1/2 minutes, 1:47 HC and 68F/20C. Speed made the difference in my case. I'm concerned about going too dilute with developers. I've experimented with very dilute solutions before and with as much SQ IN area as I run the developer depleted before completing development of the film. At high dilutions oxidation from agitation becomes a factor too. Now testing other emulsion and developers it appears that some require less of a dramatic change in time / dilution than others. Efke / Adox 50 in 1:1 D-76 required only a slight adjustment in time.

    I live in the south eastern US where our normal cold water temp is 85F in the summer and around 60F in the winter. I chill the prewet and first rinse between Dev. and Fix. I don't use an acid stop due to using Formulary alkalin fix FT-4.

  7. #7

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    Please note that you can dilute your developer of choice if needed. The drum needs a minimum of (is it 210 or 300 ml?), but as long as you don't go over the maximum of 1000 ml you're fine.
    I do understand that you want to use one (and only one) developer. It does take time to get to learn all of the different materials that we use, so it's very good advice to use one film in one developer and to print it on one sort of printing paper. Then stick with that combo until you've learnt how to get the prints you really like. Or in short, stick with Ilford HC. I've never used it (or HC 110), but I know it's good syrup.

    //Björn

  8. #8
    jp80874's Avatar
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    The good news is that I can help you find the manual for CPA-2 and CPP-2
    http://www.jobousadarkroom.com/instr...2_cpp-2_00.htm
    and the lift.
    http://www.jobousadarkroom.com/instr...cpp-2_lift.htm

    For the last three years I have been using speed setting 4 which was suggested in something I read, possibly the manual. I use it for sheet film (7x17 and 8x10) with Rollo Pyro from Bostick & Sullivan. There is a five minute staining wash and then I develop at 70 degrees for six minutes when I have shot in the sun or six minutes 20-30 seconds on a cloudy day.

    John Powers

  9. #9

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    I guess I've used HC110 or now HC for 33 years. I know the goo pretty well but have also used Rodianl 1:25 -1:1:00 and with my own mods for forty years. I used some D-76 in the early 60's and DK-50 in the 60's with sheet film but have pretty much settled on a couple of films and two developers. I like the results and predict the end product in my sleep. This is what a hundred thousand sheets and rolls of film and many gallons of the same developer can do. Years ago I owned a couple of colenta rotary processors and a merz rotary but the agitation was rather mild compared to the Jobo. It's just re thinking a new system with old developers and films. I didn't have the manual which would help but see there is a download for it now.
    In the recent year or two I have been experimenting with different film / dev combos and finding some really nice film. Back when Kodak introduced T Max films and Ilford introduced the Deltas I did extensive field testing on experimental emulsions to assist in the development of the films that finally went to market. I shot hundreds of rolls of hand coated film with various mixes of emulsion and bases. I wrote stacks of reports for both companies and made tons of prints for evaluation. In the end I never liked the original T Max films but fell in love with the Ilford enough to drag me away from Tri-X and Agfa 100 and 25. I used Deltas since that point and just in the past year or so have explored new / old offerings. In the 60's I used some Adox KB 14 and 17. Loved both but availability was limited and I drifted away until recently. Now I use some KB 25 (14) and the 50 speed. I particularly love the 50 in D-76 and have found Arista 200 superb for general shooting in sheets and particularly for platinum printing.



 

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