temperature / development time coeficient
NOTA BENE: I spelled 'coefficient' incorrectly in the title!!!
I am posting this thread in the color section because most who do color also do B&W.
I have found that with C-41 the deviation from standard temp is OK if you adjust for the development time. I get no crossover when I do this. I have settled upon using 1.05 as my factor for development time adjustment. What does this mean?
Say you get great results with 3 minutes at 100 F. If you wish to develop at 90 F you multiply 1.05 by 3, ten times. Put 1.05 into your calculator, then X, then 3, then press = ten times to drill down to the answer for 90 F. You will have a new development time of just under 5 minutes for 90 F. If you drill down to 80 F you will have a development time of about 8 minutes. With some calculators you MUST put in the factor first but, online, the calculator had to be given the current development time first.
Going the opposite direction you must divide the factor into the original time.
It works with C-41 and I have also tried this with traditional Metol/Hydroquinone B&W developers as well. It works there also. I know that, at least theoretically my offering will not hold out for all developers (maybe with D-23, using only metol this might or might not work) but I find this a great help and aid. Please be apprised of the fact that I agitate continuously during development. (This might play a part with contrast consistency because the results with '30 second' intervals at 3 minutes total development time might differ from '30 second' intervals with double the overall development time.) Continuous agitation precludes opening up this discrepancy. Importantly, this coefficient factor also (advantageously) affects needed fix or blix time as well.
Admonishments to the contrary, especially concerning potential crossover with C-41, are theoretically justified I guess, but the negatives and prints still look great and, more importantly, consistent, regardless of the time used. Here, I am trumping pragmatism over the more academic, scientific response. Thus, the inferred caveat. - David Lyga
Last edited by David Lyga; 04-16-2012 at 09:16 AM. Click to view previous post history.
Look at the images I posted of the negatives developed at different times and temperatures over in the thread about the Rollei chemicals. See if you can distinguish color crossover or not in those examples. I also haven't forgotten about my offer to test your processing methods and compare the, to standard C-41. I have the negatives processed and will make comparison prints as soon as I have time.
PE will probably want to kill me for this one.... I had a darkroom that in winter would run about 14C, I would heat everything up to ~3C above what I needed, by the time I was done development, it would be ~3C below what I wanted, C41 got this treatment, no time adjustment. Perfect results, every time.
Originally Posted by David Lyga
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WOGSTER, That is called 'pass through' temp control. It works your way and will not arouse the ire of the eminently sagacious and thoughtful (if a tiny bit bookish) PE.
I did not post this temperature factor thread to annoy him, just to 'round out' things. He is the authentic, 'non apocrypha' part of the bible of photography. But, sometimes, deviation can be successfully harnessed to pragmatism. I dare to do that. - David Lyga
Yes it WILL cause crossover, and other problems too (such as loss of saturation, if gone too far), but there is a but...
The crossover (& other errors) might be small enough that it is not visible in most images without side-to-side comparison with the exactly same scene processed normally.
And, the crossover will be small if you deviate just a little bit. A few degrees C.
Furthermore, "averaging" is an acceptable procedure; If you start with 103 F and end up at 97 F you are having a development very near to standard development at 100 F. IIRC, even The PE has mentioned this averaging thing .
The point is, why process incorrectly when you can process correctly? There might be some point to it but it's hard to imagine what. It's extremely easy to set up a water bath. Without a water bath, you may really risk running so far from the correct that the problems might get really visible.
You are making a good point, anyway; it's unnecessary to be scared about developing color. You will get good and perfectly usable results unless you screw up very badly. Even with a sloppy control, you probably exceed a typical minilab level.
Last edited by hrst; 04-17-2012 at 03:31 PM. Click to view previous post history.
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I can see a pay-off of time and temp if it allowed you to develop C41 at room temp which in the U.K. even in high summer might only be 80F and in other seasons a lot lower and my understanding is that crossover issues would arise at these temps. If you need a water bath such as the Jobo processors have then you might as well do it at 100F
Can the OP say whether he gets normal colour negs at 70-75F?
The pass through method is perfectly OK. You see, the errors caused by high temperature are opposite to those caused by low temperature, and in the end it works out.
But, being too low or to high can cause problems, as the process works by diffusion of developer in and DIR fragments out. This is fine tuned for each film and each chemical at the plant.
There are literally hundreds of tests to insure that you are getting the quality you deserve. I know what upsets the results. Bad temperature control is one of them.
But, do what works for you.
I hate to challenge SIWA but I have processed C-41 at both 80 F and 100 F and gotten the times to match the contrast (through much trial and error) and have obtained virtually identical negatives. The time factor I use for this is 1.05. In other words, if 3 minutes is perfect for 100 F you use about 8 minutes for 80 F. 1.05 X 3 on your calculator, then press = twenty times to drill down to 80 F. (However, with some calculators you must put in the '3' first, then the 'X' then the 1.05)
This is my experimentation and I offer no theoretical justification for anything with this (as would PE). However, it might be fun to copy my attempt and then see how you feel. As pentaxuser inferred, this can be quite a boon for saving frustration with the varying seasons' temperature changes! - David Lyga
Last edited by David Lyga; 04-18-2012 at 08:43 AM. Click to view previous post history.
You are not telling the whole story. You do not use C-41 chemicals, but rather a process involving diluted RA-4 chemicals. You may not notice a difference at diffent temperatures because they are overpowered by the problems of using the wrong chemicals.
Actually, to prove to myself that my usage of RA-4 was OK I bought the C-41 and use that as well for ongoing comparison. On this post I am referring to the C-41. But, you are correct, for film I do dilute a whopping ten times (with either C-41 or RA-4 for negatives) and add some sodium carbonate to bring back the energy. Few are prepared to believe me when I say that all is OK (and almost obscenely frugal!!!) And fewer are able to belive me that I can preserve these incredible dilutions forever with PET plastic bottles (found in the trash!). (Must be filled to the very rim with the developer.) I could never understand, by the way, why it takes about 2 cents to make a plastic bottle capable of not leaking and holding carbonation in soda and not even a twenty dollar bill can buy a film tank that does not leak!!!
Maybe theoretically you are correct Greg, but my prints do look fine. There is, however a (expected I guess) difference in the filtration needed for an optimal print between using C-41 or RA-4 for the negatives, but this is not so difficult to do. And, beware, that C-41 dev cannot be used for prints! With RA-4, for prints, I dilute 'only' five times the Kodak recommendation. (Full black (DMAX) is difficult to achieve otherwise.) For each liter of developer (either the 'five' (prints) or 'ten' dilution (negatives)) I add 10 ml (measured by volume, not mass) of sodium carbonate, mono (identical to washing soda).
I am reluctant to say all this here since I have no computer and cannot easily scan to offer 'proof' online. All this sounds fatuous because it deviates so much from what we are told. But my method does give good results: maybe not up to measured lab standards but, unquestionably up to most aesthetic ones. And I am fussy with quality. - David Lyga
Last edited by David Lyga; 04-18-2012 at 09:42 AM. Click to view previous post history.