C41 Color Processing for Dummies
By Nicholas Andre
It's unfortunate that the art of color processing/printing is disregarded. Whatever the reason, people insist that it is "toxic" and difficult. This is not true! I find it to be a quite enjoyable experience. Those who will appreciate it the most are those who have worked with Black and White printing for a while.
Before you start color work, it would be best if you had some experience with Black and White work first especially for rolling film and printing. The techniques are much the same, except color throws another big variable into your work. If you start first with B&W materials, color will seem like a logical next step rather than an entire confusing world.
Skip this section if you don't care, this explains the inner workings of color film and will give you basis for an understanding of each of the chemicals. Processing film does not require this knowledge, though it is informative.
Color film and processing is not based on some random magical mythological potion developed and horded by Kodak and Fuji which allows film to see a specific color. For those familiar with Black and White materials, you will know that film is based off of silver, specifically silver halide salts. These salts are sensitive to light, and after seeing light and receiving exposure, these salts retain that invisible "latent" image until it can be revealed, or developed.
Using the color separation method, it is possible to reproduce a color image from three frames of black and white film. You expose each frame of film through a different filter, one red, green and blue. If you print each of these images in their compliment color and superimpose them, you will see a full color photograph. This is a great demonstration for color theory.
Color film merely consists of those three integral layers of silver based emulsion. During exposure all three layers are exposed simultaneously. These layers are then developed and replaced with their compliment dyes. The dyes are originally in the form of color couplers, which are essentially invisible dyes. During development the couplers are "activated" and turned into visible dyes wherever the original silver image is developed. After removing the silver, you are left with only a dye image.
As such the chemistry for color work is almost all found in a black and white darkroom. Unlike B&W work, however, the color process requires careful control to develop each layer correctly. Development at the incorrect temperature results in nasty problems. Optimal temperature is 1/4 of a degree either side of 100 degrees F. Don't let that scare you though, if you seriously botch your film and drop to 99 degrees it isn't the end of the world. Just the same you will find that it's not hard to keep a large bin of water at 100 degrees. The only difficult thing is to compensate for the loss in between said bin of water and your tank, which varies somewhat.
The Materials include everything you need for B+W work as well as an accurate thermometer for color work. You also want a sink preferably with a tub in it which you can fill with hot water and add hot water throughout the process to keep it within the correct range. Once you get your film wound and in your tank, you're set to move on to the chemicals.
The Process Itself:
- Prewet-60 seconds (optional depending on who you ask, helps to ensure correct temperature, I would use 101 degrees)
- Developement-3:15 @ 100 degrees +/- 1/4 degree. Agitate first 30 secs and four lifts every remaining 30 seconds.
- Optional Wash/Stop Bath or continue to:
- Wash; a couple of fill+dumps to empty the bleach
- Wash for 3 mins running minimum. 95-105 degrees
- Stabilizer-a minute or two, room temp.
The developer is a standardized B+W developer which has an added color developer (CD-4) to "activate" the dye couplers wherever silver is developed. If you are not replenishing (adding more concentrate for each roll of film) you should use 3:15 for the first roll, 3:30 for the second roll, and 3:45 for the third roll on any set of chemistry. Discard after three rolls (one liter will do 12 rolls using this strategy.)
The bleach converts the silver image back to silver salts which is then washed away by the fix. Film should be relatively clear and orange after fixing, it will clear more when dried.
The stabilizer serves two purposes: first it binds with the extra color couplers to ensure stability (low fading) over time. Second it serves as a Bacteriostat (bacteria killer) to prevent the film from getting eaten by little things.
I recommend steel reels and tanks for better heat transfer. I usually temper the water bath to 120 to heat the developer to 101 or so (a microwave would work nicely) and then cool the whole bath to 101 degrees for the process. Any accurate thermometer will suffice.
Color chemistry can be bought online. For first timers try a Tetenal C41 press kit. This uses a Blix (combined bleach and fix) which eliminates the need for a second step. After the developer goes bad (turns dark tea colored,) get the developer-replenisher and Kodak Flexicolor set so you can continually use your developer and top it off. You can buy that from Adorama but shipping is expensive. If at all possible buy locally from a minilab dealer or other photo store.
After stabilizing, hang your film to dry from something. Attach a weighted clip at the bottom to prevent curling. To test if it has dried feel the bottom most tail of the film without images. DO NOT skim your fingers along the length of the film, as this will cause horrid scratches. You can tell if it has dried because the film will curl towards the emulsion side. A backwards curve indicates wet film.
Remember, film is delicate. It takes a well organized system to keep your film clean and scratch free. Cut the film into strips and file them in a clear archival negative sheets (print file or whatever, available at all legitimate photo stores.) Do not touch the negatives except by the very edge. Wear cotton gloves if possible. Dust your negatives before printing, too. If you cheat you can scan, but the REAL next step is the traditional RA-4 color printing process. I'll detail that in another post.
Should the film be boiled, water boils at 100 degrees, unfortunately you've not specified °C or °F !!!!
The International standard for measuring temperatures is degrees Celsius (Centigrade).
I specified. Is there no way to edit though? It would help...
Originally Posted by tiberiustibz
Last edited by tiberiustibz; 01-25-2009 at 12:43 PM. Click to view previous post history.
Reason: can't edit main post
Your original post was not a problem for me, but then again, I am not an Internationalist.
Originally Posted by tiberiustibz
Just a dummy question. Is temperature the most critical when developping? Meaning with developing you have to keep it withen the 1/4 degree variation? And with the following steps it is not soo critical?
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Nice write-up. I hope to try color some time, so hope you don't mind, I squirreled a copy of this away for future reference.
Thanks for the article. I just ordered 2 kits a unicolor and rollei from freestyle. I have been dev'ing black and white for about a year and would like to try my hand at color, I went to the Rocky mountains and shot 30 rolls of c-41 and E-6 to cross process. Any idea on developing times for cross processing? Im amazed at the lack of internet information on cross-processing, bleach bypass and film acceleration. I intend to use these processes, but im having a hard time finding times and temps. There certainly isn't a 'massive dev chart' out there for color users. I'm getting my notebooks ready, should have all that info within the year. Perhaps I'll at least have a chart of my successes and failures and some viable push-processing times for color films by the end of a year.
Everything in color (excluding some steps of the Kodachrome K14) is done at 100 degrees Fahrenheit with the exception of push/pull processing in film chains which cannot change the time. Cross processing means you run the film through a different process at specification. For example, if you want to run E6 film in C41 process you simply act like it's regular C41 film. This process gives you weird images, depending largely on the type of slide film used. I have never tried it. The times/temperatures don't change. Bleach bypass means you don't bleach, it will give you higher contrast and lower saturation. For push processing you extend the C41 time by 30 seconds for each stop you wish to gain. This is all very standardized between films.
Temperature is most critical in the color development stage because it changes how the CD interacts with the dyes. The temperature is less critical with the B+W developer (in E6 processing) and not critical with bleach and fix. I'm not entirely sure about washing at different temperatures but I assume that the wash is less efficient at lower temperatures. You have to be careful not to cause reticulation by changing temperatures too rapidly. Kodak does state that the Bleach and Fix steps can be carried out down to 70 degrees F, however you might consider extending the time of the bleach to ensure bleach to completion.
Peter de Groot, with C41 processing, the time is about the shortest time of any film processing, as such, you should aim to be as accurate as possible with the developer time, along with the temperature.
Even a little more time can make quite a difference, as can a little less. To push process C41 one stop, you only add 30 seconds, so you can see that if you somehow add 15 seconds to the developing stage, you are effectively push processing ½ a stop.
To ensure that my C41 development time is as accurate as possible, I use a stop bath of 2% Acetic acid solution, then I continue with the bleach step.
I would suggest that you don't run a stabiliser solution through rotary processing, you will end up with very hard to clean tanks and reels.
In fact for C41 stabiliser I take the film off the reel and drop it in curled up, or in the case of sheet film, into a tray, using gloved hands to carefully agitate and then pull out to hang up.
C41 is very easy.
That seems odd to me. Phototherm has a supply line connection for them, obviously expecting them to be in the processor.
Originally Posted by Sirius Glass
Since Photoflo is nothing more than soap, why is it hard to clean? A good warm rinse seems to work fine for me.