weird c-41 control strip results in jobo
I'm afraid I have yet another post regarding my continuing foray into controlling the c41 process in a jobo. My interest in obtaining optimum results has kept me in my darkroom developing kodak 5" 35mm control strips in two different types of jobo drum - the 3006 series drum (strip is taped to wall of cylinder) and the 2523 two roll drum. I'd like to make sure that I've recognized and mastered all the various contingencies of this process before I start developing film that counts. So far the results are not too promising. The most discouraging results are in the HD-LD spread - it's way too wide and the red channel is weak compared to the green and blue. The following #'s are my latest results in r,g,b respectively (HD-LD differences from aim)..... .02, .15, .13. So nowhere in the family of bizarre plots in the kodak z manual do they show the green channel spiking in this way. In my tests (eight so far) this is not an anomaly. The green and blue channels are consistently high w/ the green densities being as great or greater than the blue. My dmin #'s look good (-.02, -.04, -.02) or so says the tech I spoke to at Kodak. He had the following suggestions; decrease agitation and check the bleach (possibly leuco cyan dye formation). I'm already down to rotation speed 3 on the jobo (the manual suggests '4' for 3000 series drums). I'll post my results for rotation speed '1' later on this afternoon. Re: bleach....purchased at B and H two months ago, no date code on bottle, label on back in spanish, made in Brazil stamped on back label...possibly ballast for half a year on a banana boat! Be wary of this if you're purchasing chem. from b & h! I ordered some fresh bleach from a minilab supply but now w/ this storm I probably won't see it for another week or so. In the meanwhile I'd love to hear some people's thoughts on this.....Has anyone else run control strip tests on their rotary processor?
I use high agitation for Jobo drums and it works for me.
But, it does not always work well for everyone.
Your results also suggest low temperature or underagitation. In that case, the cyan layer is underdeveloped. If that is due to underagitation, then the cyan layer is not putting out the DIR quantity required, and the magent overdevelops.
There might be some silver retention here as well. If the silver is colored slightly, then it might peak and give additional bias.
There are so many problems possible here, I could wear out a keyboard on them. Just kidding, but a lot of things come to mind.
Thanks for your post PE! I'll follow your rec on this as the EK tech. did not have much experience troubleshooting rotary. I'm going to look at agitation since I'm confident I'm on target w/ the temperature. Perhaps the high water level of my bath (the opening of the "mouth" is dialed in at 9 o'clock) is causing drag on the 3000 tank and already lower than normal rotation speeds? Underagitation would also account for the underactive bleach and fix stages of my process thus the problem being compounded by silver retention. Besides, I'm not certain, but isn't c-41 bleach a rather robust chemical in terms of its shelf life in an unopened bottle? Even it comes from Brazil what are the possibilities of it going bad? When you write "high agitation" are you referring to the 'p' setting on the speed dial?
I use the high agitation on my Jobo, which is P and is recommended by Jobo due to the drag caused by a heavy drum filled with chemistry.
Bleach keeps well and has a lot of capacity.
Just make sure that the pH is about 6.5. Kodak even says that you can use a 2% acetic acid stop after the developer for up to 1 minute at 100F to protect the bleach and insure rapid cessation of development. See their web site for information.
I've run control strips in my 2513(?) tank with a single 5x4 reel on my Jobo CPE-2. I used the high agitation setting. My densities were all within 0.05 of the reference.
I used home-mixed chems and the formulae posted elsewhere on this site.
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ok...so I cranked up the rpm's to "p", changed my temp +.1 c, used a two step prewash to make sure I was up to 100 degrees f. (total 5 minutes), and added 30" to both the bleach stage and the fix stage.
5'...two step prewash
7'....Flexicolor fixer and replenisher (mixed for the working tank solution, not replenisher solution)
The control strips from this recent batch yielded the most exaggerated example of the trends that I've been noticing all along....
Dmin -.03, -.04, .00
LD -.01, .03, -.02
HD-LD .06, .27, .19
What's weird is that my control strips for the small 2 reel 35mm. tank are much more on point. Same chem., same batch of control strips, same drkrm., same speed on jobo ("p") and same batty operator. Check it out...
Dmin .01, -.03, .01
LD .01, .02, .01
HD-LD .02, .07, .02
Based on these results I'm thinking two things...the 3000 series drum is causing more agitation than the 2500 two reel and thus causing a spike in the green and blue readings (don't they move the fastest when over-developing?)....also, maybe the fixer working tank solution is too dilute for rotary processing, being approx. 85% the strength of the replenisher solution. IDK...maybe there's a problem w/ my rotary speeds, either too fast or too slow. I'll try it at a slower speed later on to compare results.
PE...is there a simple technique to check pH on my bleach? Also, not having any 2% acetic acid will Kodak indicator stop work ok?
Thanks for your help....I'd feel completely in the woods w/out this forum!
Overdevelopment affects Yellow and Magenta more than Cyan. This is correct. Overagitation does the same.
I'm at a loss to explain this.
Are these Kodak control strips? Have they been kept well? Are they out of date? I ask this to get more information.
A suggestion is this. Take a photo of a macbeth color checker and run through the process. Read the density of each step in the neutral step scale. Taking into account the offset introduced by the dmin, you should get 3 parallel lines if you plot step vs density. If this works, then the test strips are off, if you see the same magenta bias as you do in the test strips then something is seriously wrong here.
Yes, you can use Kodak indicator stop diluted as stated on the label.
Is this causing problems? Chemicals not getting behind the film? Just guessing
Originally Posted by frotog
Yes, Kodak control strips - the five inch 35mm kind. I've taped them to the inside of the barrel on the 3000 series drum. The first tests I ran were w/ recently expired strips (this month). To rule this factor out I purchased some fresh strips and alas, same trends as w/ the older strips.
If, overdevelopment and overagitation affect Yellow and Magenta dye layers more than the Cyan then I should try less agitation right? After all, the aforementioned results w/ the two reel are significantly closer to aim. The film in this tank is nearer the center of rotation and so less agitation than w/ the 3006 drum. Another consideration...perhaps the speed dial on my cpp is setting the rotation speeds faster than the factory presets.
I have an old xrite 810 and an equally old trans. calibration strip that's kind of scratched up w/ use. Am I correct in assuming that because I'm comparing deviations from measurements made from the reference strip and using the same machine to make all the measurements, the measuring device should not be an issue?
Unfortunately, no macbeth color checker but I do have the 14" Kodak color control patches as well the kodak gray scale that came w/ it. The color patches are laid out in two rows, a saturated row and a less saturated row of the same color on top, in bl.,cyan, green, yel., red, mag., followed by White, 3/color, and then Black. Would this work for the test you prescribed?
I'm waiting for a fresh stock of bleach and fix to arrive. I do have another developer kit I could stir up inorder to rule out faulty developer. Meanwhile, I'm ready to descend back into the saltmine for further testing at lower rotation speeds....
Nick - the emulsion side is facing out...does the acetate side need chemical activity? The strip is taped on either end leaving the long side pushed up against the wall of the drum so as to mimic the curl of a sheet of film. Also, I'm providing ample prewash time. However, in the test I'm about to run I'll let one of the control strips loose in the barrel of the 3006 just to make sure that this is not an issue.