A little E-6 help needed
OK, so I am having this problem with a blue (slight) color cast when processing 8x10 transparencies on my Jobo CPP-2 processor.
I am using Kodak chemistry and mixing according to the instructions. Times and Temps are accurate. I am using a 60% working solution on my reversal bath as per Jobo's instructions. Plenty of rinses between chemicals (except between reversal bath and color develper) so contamination shouldn't be a factor. I am using Ektachrome 64T under tungsten lights (3200k) and checked the color temp of the lights (they are right on).
I've processed hundreds of 4x5 transparencies using the same chemistry, same set-up same everything....except the processor is a Photo-therm. No problems.
I've mixed up new batches of chemistry, checked and re-checked temps, nursed the processor along, said a few prayers and still the problem rears it's ugly head.
I really hate burning through 8x10 film and having to re-shoot the job over and over, but the color has to be right on.
Any of you E-6 guru's out there who may have some suggestions, please don't be shy!
I've processed miles of ektachrome in different types of machines (although not the CPP-2) I've never had much luck with one-shot rotary processing but in dip and dunk and roller transport seasoned replenishment systems, a blue plot usually indicated a Ph problem in the color developer. A small (TINY!!!) addition of sodium hydroxide was the prescription.
But, if your 4x5 is coming out consistantly good I can only think that it might be the emulsion batch of the 8x10 film.
Neal's suggestions are good ones, but if you've processed film from this batch and it's been okay, then that would answer the emulsion batch question.
Other issues could be--are you using longer exposures than you usually do for these shots, and possibly getting a reciprocity problem? Is there some daylight from an unshaded window getting into the shot? Is it possible that the water has changed (municipal water systems might up the chlorine in the warm weather, for instance)? Have you actually checked the pH of the solution? Have you tried just filtering (the lens, not the water) your way out of it?
try adding about 10ml of sodium hydroxide 5N per liter and a half of the color developer. you can adjust the rate higher or lower if needed as well, but it doesn't take much. diluting the reversal bath also helps, you can also monkey with the first wash temp to warm up the color balance.
I find it neccessary to add sodium hydroxide to every batch of chemistry (kodak) we use for our wing-lynch machine at work. for years, we ran the rev bath at 60% and then kodak advised to use it at full strength with the newer chemistry. we had nothing but problems this way. after much tinkering with our control strips and process--we now have almost perfect plots. I have never seen them better, and both EPN and Provia run great.
here's what we did: put the prewet back into the process. diluted the rev bath to 60%. added 10ml sodium hydroxide per 1.5 liters. extended the final wash 5 minutes extra.
If you overshoot the balance on the sodium hydroxide--you can shift it back with sulfuric acid. You can eyeball this if you aren't using control strips. Since you shoot EPY--if you can get any (fresh) of the old control strips, they'd be perfect, since they were on EPY stock. The newer ones, are more sensitive and don't have the same control measures really. The sodium hydroxide works more on a cyan type balance. It's not used to bring the blue HD plot up anymore. As far as I can tell, the reversal bath concentration seems to be more of a control here, but you afe already diluting this, so I would try the sodium hydroxide.
btw--you mention using washes between the steps except for rev-color developer. you shouldn't wash between the color dev and pre-bleach either, if you still do this? the pre-bleach needs the carryover color developer for stabilization.
hope this helps--go to Kodak's process control website and the Z-book and much of the control stuff is free online now.
Before you do anything check this out!
If you have a blue cast to the transparencies, is the border also blue? If so, it is as stated above, a process problem (or perhaps a bad batch of film). If the border is black, but there is a blue cast to the image it is more probably an exposure problem. This could be either your error or it could be a slight deviation in the speed of the film itself and can be corrected by a yellow CC filter. It will be hard, in this latter case, to separate out a slight exposure error from a slight speed deviation of the film.
Use of a color temperature meter will help determine which of the latter it is.
Don't make changes to the solutions until you check out the border. If it is a true process problem, the blue color cast will extend into the border. In fact, blacks overall can look thin and blue.
I appreciate the responses and advice.
Neal, as you suggest, I haven't ruled out a possible film issue. I did process some 35mm transparencies and checked for a color cast. It's much harder to see, but I think the problem still exsists. I ordered some Sodium Hydroxide...
David, my exposure times are 5 seconds or less (bracketing) so I don't think reciprocity failure is coming into play in this instance. My exposures look pretty good, but I know that reciprocity errors will play havoc on color. One point you made about the PH of the water.....very interesting. That is a point that deserves further investigation.
KT, while I'm waiting for may Sodium Hydroxide to arrive, I am going to give your suggestions a try. I have been very careful to rinse between each step to avoid cross-contamination of the chemistry and haven't been using a pre-wash at all. The Photo-Therm processor use's a pre- wash/wet before the 1st developer. I'll give that a try in the Jobo. Also, your suggestion of no rinse between the Color dev and the pre bleach is worth a shot.....never tried that. Never even heard of it. Learn something new everyday. This should be fun.
PE, the blue (cyan) cast does extend into the blacks and borders. I've measured the color temp of the light source and it is 3200k and even. I am using a cross polarization technique to avoid reflections etc. I am shooting artwork (paintings) and the color has to be right on. Typically, I bracket in 1/3 steps to really nail the exposure (3 shots) and have found that using this technique saves me time and expense in the long run. the yellow CC filter is an option and I haven't ruled that out as a last ditch effort if the other changes I will make don't pan out.
I'll keep you posted on my progress, and again, thanks for the help!
Rick--there used to be that wash in between the color developer and the conditioner, but Kodak changed that about, I dunno, 5 yrs ago maybe when they ditched the stabilizer. you may remember using the conditioner before the bleach? Now, it's prebleach and the final rinse is like photo flo almost. Apparently the stabilization takes place in the pre-bleach now and is triggered by carryover of the color developer. So, if you wash in between the two, this undermines the stability.
It's a bit of a PIA in the processor we use as well--since it's automatic and we use an older process card (program). We have to manually step over this wash cycle, but otherwise it's still automatic. Kodak also says that the prewet step will throw off the process control and make it harder to acheive consistency, but we've run numerous control strip tests, and actually have much smoother plots with the prewet, than without, so to each his own....
like I said, our plots now are perfect & the film looks great, but if we mixed the chemistry like Kodak says to, right out of the box, they'd look much different.
Not rinsing between the color developer and pre-bleach did the trick. Getting great results now....without the sodium hydroxide.
Thanks for the help guys, Rick