Colour pictures from black & white film

Long ago, before there was colour film, it was possible to create full colour pictures using black & white film with a set of coloured filters. This is exactly how three-strip Technicolour works. For movies, you have to use a beam-splitter to split the image into three. Each image is then passed through a different coloured filter (red, green or blue) and hits a different strip of film that is running through the camera.

Technicolor three-strip
Technicolor three-strip

For still photography of stationary subjects, we have the advantage of time and the three pictures can be taken one after another. I’ve been thinking about trying the technique for a while and finally got round to it this weekend. I set up a colourful scene on my table. I chose the boldest colours I could think of – a casino set with coloured chips. I couldn’t think of any good reason why I shouldn’t use an outlandish camera, so I set up my Horseman 45HD with Schneider-Kreuznach 150mm f/5.6 lens. I’m not completely insane though – rather than use 5×4″ sheet film I decided to go with my “crop back” which takes 6x9cm roll film.

Setup shot
Setup shot

I know doing macro with large format camera needs lots of light so as well as using the light from the window, I set up a 500W halogen lamp. Once I had taken into account the bellows extension factor, reciprocity failure of the film and the filter factor, I came up with an exposure of eight seconds at f/8 on Ilford FP4+. I shot the same scene three times, once through each filter.

RGB filters
RGB filters

When the film was developed, washed and dried, I scanned it in black & white. The three pictures look quite similar at first glance, but at closer inspection there are obvious differences between them. Coloured filters make their own colour appear paler in black & white, so in the red picture, the red markings on the cards appear almost white.

I combined the three images in GIMP using the compose tool. The stacking itself is easy enough but you have to make sure your source images are exactly the same dimensions and positioned correctly. Mine weren’t, due to the slightly shonky film advance. Five minutes of alignment and cropping and I was ready to go. Here’s the final product.

Three-colour image
Three-colour image

It works! The green and red colour fringes on the nine of diamonds shows I didn’t get quite get the alignment perfect, but it’s pretty good. The colours are a bit “off” presumably because my filters are cheap and aren’t perfect saturated red, green and blue.

The blue tokens have rendered nicely. The red and yellow ones are a bit faded, while the green felt is quite dark. It does look like a scene from an old movie. I’m very pleased with the effect! This is definitely one to try again.

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