By Paul Williamson

18 June 2007

Cross processing is a technique where you develop a film in incorrect chemicals. Most commonly this involves taking slide film (E6, or reversal film) and processing it in regular negative (C41) chemicals. This results in unpredictable colour shifts and insane contrast. This usually also increases the amount and size of grain. So why would you want to do this to your film? Well, for a start its a great way to add interest to colourful or unusual images. The effect may not be to everyone's taste but I find it works exceptionally well with gritty urban subjects. Graffiti, decay, and neon signs are all ideal candidates to be cross-processed.

So how do you get the most out of crossing? The key here, as you have probably guessed, is experimentation. There are so many variables with cross-processing - exposure, film type, the chemicals your film is developed in - that you really do have to shoot a few rolls to find out what works for you. There are a few common colour shifts that are a good place to start. Fuji Sensia tends to turn you images a green/cream colour, Velvia 100F injects some intense red, and Agfa Precisa focuses more toward the blue side of the spectrum.

Here are a few tips to get you started: ask your lab for no colour correction on your prints to get almost monochrome colour shifts. Under-expose by a stop or two to reduce contrast. Save money by buying expired slide film - expired film tends to shift colour-wise, but this usually adds to the effect of cross processing. Try as many different types of slide film as possible until you find one that's perfect for you.

So what about other types of film/chemistry? Well, running C41 through E6 chemicals results in flat pastel colours with very low contrast. As a result you may want to over-expose, or tell your lab to push-process a few stops to compensate. If you process colour film in black and white chemistry, you end up with sliver-based negatives. As colour film is usually more expensive than black and white, this technique is a bit pointless!

Have fun and good luck!

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