Colour Experiments in Black and White

Inspired by old Technicolor 3-Strip colour film processes, an urge to process colour images at home and a free weekend; i decided to live it large and produce some colour images using only black and white film.

The principles are simple; a colour image can be photographed and re-produced by recording luminance values of the primary colours of visible light Red, Green, and Blue. This can be done by shooting 3 frames of the same scene onto black and white film, each one filtered to isolate Red, Green, or Blue; then scanning each frame and applying them as the appropriate colour channel in a RGB image in Photoshop.  I did this using three Lee polyester filters: 25 Tricolour Red, 47B Tricolour Blue and 58 Tricolour Green. Each of these filters completely isolates the single colour by filtering out all other wavelengths. I measured the transmission levels of each filter with a spot meter and used NDs to balance them, so they needed equal exposure compensation. I then mounted these filters in a row on some card to make them a quick as possible to change.

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I shot the first test on a Hasselblad 500 with a motor winder to make the time between exposures as short as possible; i used the 5×4 camera pictured later.

I chose Kodak T-Max 100 for it’s fine grain; the final image having three layers of the emulsion i wanted to minimise the grain. The film was processed normally in Agfa Rodinal.

RED FILTERED IMAGE

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GREEN FILTERED IMAGE

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BLUE FILTERED IMAGE

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After scanning the three images i created an RGB image in Photoshop and imported the three scans in as separate layers (make sure they are all separate layers and one is not the background layer). In the layer blending options (ctrl click the layer and select blending options), i assigned each image as the correct channel under advanced blending.

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It is important to keep track of which image is what colour throughout the process….and that is basically it; i now had a full colour image. A little moving around of the layers to get the channel alignment as good as possible (it will never be perfect due to the time between exposing each image) and lifting the levels a bit produced the image you see here.

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