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.
home mixed c-22 bleach is great for c-41; it bleaches in about 2.5' at 38C for me, and can be reused and replenished, and is stable when kept in glass in a cool dark place. Filter it after every dozen rolls; it gets very black.
I mix it 80g K Ferricyanide and 20 g K Bromide per litre, but I have seen other formulae where these weights vary somewhat. I would mix 45ml of fresh into the working to keep activity constant, and discard when a litre of replenisher has gone in was my rule.
I found a ton of e-6 bleach and have been using it up for c-41 at 6' 38C for 25 rolls unreplenished. When it is gone I will be back to c-22.
my real name, imagine that.
Remember that the C22 bleach is so strong that it can oxidize some components of C41 films. So, be careful! C41 films contain some level of antioxidants to preserve the dyes. Also be careful when using the bleach because you must stop, clear and wash after the developer and before using the bleach. You must then wash again before going into the fix.