Realising that I could replicate this technique without having to purchase any extra equipment or chemistry, I gave it a try. Why, you ask? Because I wanted to see how it would work in today's age of digital cameras and Photoshop - and it has a certain novelty to it. Please note: this technique can't create a colour photograph from an old B&W negative - the method only works if the original negatives were photographed through coloured filters.
Here's an easy guide for those that want to experiment with this technique:
You'll need:
• A film camera and some B&W film, or any digital camera.
• Red, green and blue filters. Doesn't need to be screw-in filters - coloured gels will also work (perhaps multiple layers of cellophane will also work?)
• A tripod or somewhere sturdy to place the camera.
• Adobe Photoshop
I decided to use my DSLR, but any digital or film camera will work. Set the camera to B&W mode and compose your subject. Get your filters ready, and then take three photographs - one for each filter. In order to remember which photograph matches with which filter, shoot in the order of red, green and then blue, i.e. RGB.
Transfer the three captures to your computer. Export JPG files if you shot RAW, and name them Red.jpg, Green.jpg and Blue.jpg. Open all three images in Adobe Photoshop, and copy them into a new document as layers, once again naming them accordingly. As the photographs were taken at different times, they might need to be lined up as well. Double click on a layer to bring up the Blending Options. On the first pane, under the Advanced Blending field in the middle, untick the channel selections that don't apply - leaving only the "R" channel ticked for the red image/layer. Once you've done this for all three layers, you'll have a colour image! First thing you'll notice is that the white balance and exposure might be off, so add a Curves adjustment layer to fix any issues. That's it! You've just made a colour photograph using only black & white source images. Extra props if you do this using scans from B&W film. Below are some examples:
Example 1
Red-filtered photograph Blue-filtered photograph Composite image Adjusted image Example 2 Red-filtered photograph Green-filtered photograph Blue-filtered photograph Composite imageAdjusted image