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Article on Home Processing C-41 Color Negative Film

  1. Hi guys,

    Like many of us, I process my own film and (i) I am not processing high volumes (maybe one roll per week on average), (ii) I want to process the film as quickly as possible after shooting, (iii) I do not want to compromise image quality and (iv) I want to keep the cost of processing as low as possible.

    With less than a year of experience and only about 40 rolls processed I am still very new to developing C-41 but I wrote up an article on my blog summarizing what I have experienced/learned and how I go about doing it. I am using Tetenal Colortec C-41 kits because that is what I could get my hands on but most of the process would be similar with other C-41 chemicals.

    Link to the article: http://photo.fleurey.com/blog/developing-c-41-color-negative-film

    The main takeaway is that I really recommend developing at 30°C (an not 38°C) and that with good care it is possible to reuse the chemistry for more than 10 batches over several month without risking image quality.

    I hope it contains some useful information for some of you and I am of course grateful for any feedback if you have suggestions on how I could improve my development technique. Let me know what you think!


  2. A very good article, Franck. What I especially liked was your explanation of your tests and the sets of negatives and positives to illustrate your conclusions.

    Does Tetenal gives times for temperatures less than 30C? If it does it would be interesting to see if there were any differences in quality at even lower temperatures

    There are those who will say that processing at anything less than 38C results in lower quality or the dreaded colour crossover but you negs and positives would seem to illustrate this isn't the case

    This will give hope to those who want to try home processing who do not have a temperature controlled processor and who worry about the longevity of chemicals if there are low volume processors of C41

  3. Good article, but there are significant differences between "normal" and "changed" process conditions that include the color dmin being changed, the density and contrast of the negatives being changed, and etc.

    So, if you "accept" those changes, that is fine. I don't and will not make compromises in my images and then "fix" them to be nearly equal. I am losing some of the information that I worked so hard to build into that film.

    In spite of your examples, you have agreed in the text that there are differences. If you like those differences, that is on you, but if you don't, then stay away from this process.

    Oh, and this begs the question of how the Tetenal kit you use differs from that of Kodak or Fuji, and how different films respond to this. Remember that all color negative films are put through the C41 release process, and may vary widely when processed as in your article.

    I hate to be such a harsh critic, but it was hard making all of those films "sing" together in one process and one time of development.

  4. The reason for the 38C (100F) temperature is not just for short developing times. You will get crossover and potentially other problems at other temperatures. The pics shown are not good ones to demonstrate this, but in any case they are scans and cannot be relied on.

    The main question of developing C-41 at non-standard temperatures is not will there be color degradation (which there will be), but is it acceptable to the user.

    EDIT: Looks like PE and I were thinking and posting the same thing at the same time!
  5. Hi guys!

    Thanks a lot for the good critical feedback. I suspected that the most "adventurous" part of the process I am using is the low temperature alternative.

    In terms of what Tetenal recommends, there are 3 alternative temperatures: 30°C, 38°C and 45°C. According to the instruction manual the only difference when processing at those different temperatures are the times, there is no mention about any differences or trade-offs in the processing results. Of course that does not mean that there are no trade-offs but I hope that if a major difference was to be expected it would be mentioned :smile: The only was to find out would be to do some tests...

    Just like you guys, I am not willing to accept any degradation of my images and my main reason for developing at 30°C is to get the best possible results, not convenience, cost or anything like that. Let me try explain what I mean here.

    There is no such thing as a perfect, normal or standard process. Whatever camera, film, chemicals, temperatures, times or agitation we use, all of those are less than perfect. Think about the exposure, yes we work hard to get it perfect but most cameras have 1 stop exposure increments, we do not use the T stop of our lenses, etc... In the end we just have to acknowledge that at best there is a 1/3 to 1/2 stop margin. In terms of film, there are variations between different types of films but for the same film there are also variations depending on batches, the age of the film and how it has been stored. Again we have to acknowledge and live with those differences. Same for the chemicals, there are going to be variations between brands but also batches from the same brand, exact dilutions, aging of the chemicals, etc... We do all we can to minimize every difference we can control but again it is never perfect. For the temperatures and times, we try to be very consistent but there are variations. For temperature, the higher is the temperature difference with ambient and the bigger the error we will make. For time, the shorter the time the biggest the error.

    You may disagree with one or the other of my examples (and there could be a debate for each of them), but overall the point I am trying to make is that, as a matter of fact, there are a lot of non avoidable variations no matter what process we are using and no matter how consistent we think we are. Can we agree on that? This means that there is nothing like the perfect, normal or standard result, there is a range of possible results which are considered "within specification".

    I am interested in finding the process that gives me consistently the best result possible from the film I have shot. Some aspects like exposure, batch of film, age of the film or chemicals we cannot control but for what we can control the goal is to find the most consistent combination. My current hypothesis is that the small error we make on time and temperature when using 3'30" at 38°C will produce more changes on the result than the changes related to processing at 30°C vs. 38°C. Another way to formulate it is that is easier to stay "within specification" at 30°C than at 38°C.

    So far, I have not found any hard evidence proving or disproving this hypothesis, but I have found instances of people getting more consistent results at 30°C and no instances of people showing the opposite (even if there are a lot of non quantitative claims out there). That is why I have chosen this temperature but I have no strong feelings about it and would be happy to use 38°C if the inevitable amount of over/under development at 38°C produces a smaller change than the processing at 30°C vs. 38°C.

    At some point, I think I will have to make an experiment to have at least one comparison between film developed at 30°C or 38°C. What do you think the result would be? How would you go about doing this test?

    Could you be more specific? If I decide to go ahead and do some testing what kind of pictures could show the most dramatic differences? Something like saturated colors in shadows?

    I'd like to point out here that all the examples that I have posted have NOT been processed/fixed in any ways to look equal. For every comparison, both negatives have been scanned or photographs together and exactly the same processing has been applied to both. Is that the issue you are referring to or is there something else I am missing here?

    Sorry for the long post. I hope this makes at least a little sense :smile:


  6. ++
    I think the most important thing, is whatever the water used, method of agitation ect, that each person has to do it in as a 'perfect' consistency as possible, including the developer, until one gets the best results with the time that is required for their personal liking of the negatives. In B&W this is simpler. In color as PE & RPC have stated it is not as easy.

    I don't do that much color development, usually the most in spring.. and here we are... but consider myself a newbie, with little experience with color, but you make a very strong point and looking forward to your experiments.
  7. Photograph a Macbeth color chart over and over to complete a roll, then cut the roll in half. Process one half at 38C and the other at 30C. Scan without any correction, you should see if there is any difference.

    Somewhere there is a thread where I put the Digibase brand kit under this type test. The results were shown for all published temperatures that came with the kit.
  8. Hi, in professional photofinishing the standard test would be to process what they call a "process control strip," which is pre-exposed by the manufacturer. Then you use a densitometer to compare your test strip to one which is ideally processed by the manufacturer. This "reference strip" IS the ideal goal. I think that your off-temp process has almost no chance of being within spec limits. Now being outside of the limits doesn't say anything about how the prints will look - it's more of a statistical tool.

    Without process control strips, I'd say that you almost have to carry the tests forward to optical printing. The sort of work I've done most has been portraits, and I'd say you're doing pretty good if you can get good color on a range of flesh tones, from highlights to shadow, PLUS neutral reproduction of some included gray scales (in the photo). The main problem with the subjects you are using is that the colors are open to interpretation; no one knows exactly how they SHOULD look. So if there are color "errors," they're not obvious. In the case of skin tones, color errors will stick out, at least to a trained eye.

    Since you aren't doing your own enlarging, here's what I'd suggest. Shoot a couple of duplicate rolls of film including portrait subjects and neutral test scales (a Macbeth ColorChecker works fine). Process one roll yourself and have a "known good" pro lab do the other. Then have the same lab optically print some photos from BOTH rolls, matching the color between both. Once you have both side-by-side, it's fairly easy to see differences. I'd guess that your off-temp process has almost no chance of matching to satisfy a critical eye. But this is a good education in how to examine photos, especially if someone from the lab goes through this with you.

    Since you scan your film, all the above probably doesn't make much difference to you. So I'd just say keep on with what satisfies YOU, but be careful about telling others that the film is well-processed UNLESS you actually confirm this. Best wishes and continued success!
  9. There is always some "auto correction" when you scan a negative image, whether you know it or not.

  10. Franck, you are concerned that 38C will not give the consistency of 30C. I have experimented with low temperature C-41 processing. My tests consisted of photographing gray scales and measuring for crossover with a densitometer, and visual tests as well--printing those gray scales as well as skin tones.

    With 100F (38C) I consistently got (and still always get) densitometer measurements that are within Kodak specs, meaning acceptable crossover. But with low temperatures, I also got consistent results, but consistently out of spec! The lower the temperature, the more out of spec. This was always noticable to some degree in the prints. As I said in my earlier post, it is up to you whether it is acceptable.

    Those who scan their negatives can correct crossover with appropriate software if they are skilled at doing so. On the other hand, processing correctly means you don't have to. Those who print can make no such correction, so they are stuck with inferior prints.

    If you are going to promote using low temperature processing I suggest that you give your audience the caveat that I and others have, that the results will be inferior to some degree to the correct process, but suggest that they try it, and see if it is acceptable to them, as it is to you.
  11. Thanks Greg, I managed to find one of your post with some of the images here (there was a url link here which no longer exists). Nice set of tests and the difference between temperatures is indeed visible. Beside this post have you published a more complete article? (you mentioned it in another of your post but I did not find it with a quick search)

    Indeed, what I do is that when I compare two negatives, I scan them together (i.e. on a single image) so that whatever the scanner applies as auto-corrections, I am sure that it is the same across the two images I want to compare. Then I can crop-out the two images to compare (that is what I have done for the comparison posted on my blog). That should be ok to see any kind of differences, right?

    That really made me want to gice 38°C a try. I just developped a piece of my test roll of film at 38°C for 3'30" with the rest of my usual process unchanged (but of course all at 38°C). It is now drying. I can't wait to see how much of a different will show compare to my 30°C control strip. As discussed before, the pictures are really not ideal for the test but that is a cheap and easy test I can do right now so let's see what we get!

    Thanks, that is a more proper test with a more absolute reference. Now I need to find a "known good" lab :smile:


  12. Hello!

    I have looked at the results of my little test developing a strip of film at 38°C instead of my usual 30°C. As you guys indicated, there is a quite big difference.
    I have written up a post with all the images and details, it includes a zip which you can download to see good resolution images.
    It is here http://photo.fleurey.com/blog/processing-c-41-at-38c-vs-30c

    In short, I could see a significant difference in color balance and in the density of the negative. It is just a single test so it is hard to know how much of the difference is due to the temperature and how much could be due to me not having the exact right timing or temperature. I will switch to developing at 38°C for a while in order to see how consistent results I will get.

    In the blog post, I voluntarily did not mention which strip what developed at what temperature. Can you guess? Does one look better than the other to you?


  13. In your new scans, the sky in the leftmost frame is always bluish in the upper strip, and slightly greenish in the lower strip, making me suspect that the upper strip was developed at 38 degrees. Is that correct?
    But as (I think) PE mentioned, flesh tones are are difficult to reproduce accurately, making them a good test.

    Mark Overton
  14. I tried the cold C-41 thing and found the colors were off so far I couldn't satisfactorily correct them in photo shop. Also, the added development time was more than the time it took to heat the chemicals to 38*c

    I understand the cool temperatures are supposed to help the developer last longer, due to less oxidation but i couldn't get over the color shifts. That killed it for me.

    I do use cold c-41 on old C-22 Kodacolor-X, just to get any color at all out of it and can accept the shifts for those rare rolls of found film
  15. Hello!

    Thanks for your replies, explanations and advice. I have been quite busy and I have not developed any new color film as yet. Maybe I'll shoot a roll today, we will see :smile:. Anyway, just to give the answer to the previous questions, the bottom strip was developed at 38°C. There are indeed some differences in the color of the sky, I had not really noticed it.

    I'll post again when I will have developed a few rolls at 38°C. Now I am actually hoping to see an improvement over what I am used to!