Home Process C-41

November 3, 2012

C-41 is the process used to develop colour negative film. Traditionally this has been done by both minilabs and pro labs. It’s a simple process and not difficult to achieve consistent good quality with a bit of care. I’ve avoided minilabs for my C-41 processing as they use roller transport machines which can scratch the film if not kept clean. I know of three good pro labs in Sydney and I’d be happy to give my film to any of them, however I have recently had a go at processing my own C-41. I’m very experienced with black and white processing – I probably develop ten or so rolls per week, so processing colour film only required a slightly modified approach.

There were a few reasons why I decided to try processing colour myself rather than using the lab – 1: Convenience – the labs I use all require driving to areas where I don’t have any other reason to be. 2: Cost saving – the average lab price in Sydney is about $8 0r $9 per roll, whereas developing myself works out at about $3 or $4 each. Also, some of the rolls were from a Diana and I suspected they would have light leaks as well as the usual number of frames that are crooked or just not interesting and it is more palatable to be paying a few dollars per roll for this. 3: Just for the hell of it – to get a feel for how practical it will be as an ongoing system and also to find out if I could produce quality similar to a good lab.

I used a Tetenal powder kit that mixes to make one liter stock of the three solutions that are required. No retailer in Australia had stock, so I had to buy from overseas. I would have bought a liquid kit but I was purchasing from B&H in New York and they are not permitted to ship the liquid chemistry by air so I had no choice but to get the powder. Mixing the chemistry is easy and the kits come with clear instruction sheets. It’s as simple as mixing the powder with hot water in clean containers and then storing in clean jugs. I used plastic two liter milk containers that were rinsed with hot water first. I did all the processing in the standard Paterson tanks using the agitation method. I did half a dozen or so sheets of 4×5, a couple of rolls of 35mm and about eight rolls of 120.

As a control I had one roll of 120 and one sheet of 4×5 processed by a pro lab. These were selected from shoots where I had similar rolls and sheets that I could process myself. Above is a direct comparison of my processing next to the lab’s – you can click on this to see the full size image. Both sheets were exposed at the same time with Fuji Pro 160 S in my Crown Graphic. The exposures were slightly different – one sheet at f/11 and the other at f/8 both at one second. This was bracketing as I wasn’t sure about the reciprocity failure characteristics of this film. At that time I wasn’t planning to do this processing comparison or else I would have exposed them the same. Having said that, there is only a one stop difference which I think is not significant for such a comparison.

Both sheets were scanned on the same Epson V700 scanner with the same basic settings. The results are close enough to identical and assured me that I could process C-41 to lab quality. The key factor in colour quality is the processing temperature which has to be at 38 C (about 102 F). This is trickier than B&W which is done at more or less room temperature, and where the time can be varied if the temperature is a bit hotter or colder. With colour you have to get the dev to the right temp and keep it there for the 3.5 min developing time. I used the rough and ready method of having a 20 liter container filled with water at the right temp and sitting the dev tank in this when not agitating. This worked OK but next I will research a cheap and simple heating method such as an aquarium heater or slow cooker to get more stable temperature. I found the info at this link useful when researching what products to buy and what approach to take, and recommend it to anyone considering processing their own colour negative film.

The processing was done two weeks ago and the number of rolls has slightly exceeded the given capacity of the chemistry with no deterioration in quality. Storage time will also have an effect on chemistry strength due to oxidation. I do intend to keep processing in this mix until the results are obviously unacceptable as a result of either exhaustion or deterioration. I won’t risk any important film and will do clip tests first. For my next purchase I will try some liquid chemistry which can be shipped from Europe and mixed from concentrate as required.


One Response to “Home Process C-41”

  1. Excellent work, well done. C41 is really easy, I don’t understand why more people don’t do it.

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