You'll remember that colour neg and reversal films are made up of three layers, sensitive to red, green and blue. Each of these layers can be exposed separately by putting red, green and blue filters over the lens in turn, although the actual sequence doesn't matter. Tricolour filters work best, but any strong filter may work ok. You need a camera that allows you to do multiple exposures on the same frame and setting up on a tripod is a good idea, at least until to get the hang of it all. Testing is needed to get the proportion of each exposure right and avoid undue colour casts. Start with the filter factors indicated on the filters. Why do it? Well, after all three exposures anything that hasn't moved will record fairly normally, but anything that has moved will be a mixture of colours depending on the amounts of red, green and blue recorded. Lets take an example. Photograph a beach scene of sand, rocks and waves lapping against the shore using this method. The beach and rocks stay still and come out normally (unless you're in California at the wrong time), but the sea, birds and people moving in the shot will appear as a mixture of colours. Surf will only appear white if it happened to be there for all three exposures. Unpredictable, but can be interesting for the right subjects. Yes, you can do it in Photoshop if you like, without all the filters and multiple exposures, by taking three shots on B&W film and using each as a separate channel in an RGB file or swapping about the channels in three separate colour shots.

Large grain is something that you find easy to get when you don't want it and hard when you do. The main problem with large grain is that it reduces the detail in the image and so is not suited for all subjects. Firstly, use a fast 35mm film that already has a large grain size. Try Kodak T-Max 3200 and Recording Film or Fuji Neopan 1600. One way is to then up rate the speed of the film and push process it. This increases the contrast and gives the grain more time to grow. Kodak Recording film was originally made for photographing instrument panels back when instruments meant dials and lights and it's easy to fog by over-development. Another way is to use print developer, but you will need to do your own tests for development time. Start with the same dilution as for printing for the developer you're using and a dev time of 4 minutes. Expose a roll of film of the same subject from two stops over the indicated exposure to three stops under. Go in one stop steps for starters. Then the film can be easily chopped up in the dark, using a ruler with rubber bands on it so that you can feel the approximate length to cut. Set the length using a strip of processed negs as a guide. A few frames will get wasted each time, but a 36 exp film will give about five test strips, probably enough to decide the best time. What ever method, avoid having a wide brightness range in the subject. The contrast of the image will increase in the development and if the grain is allowed to block-up in the highlights, it will not look so conspicuous. Also, when framing the shot, keep the subject smaller in the frame so that you have to enlarge more to get the print size you want. Check first how far you can take this before running out of enlarger movement.

© Barry Leighton FRPS