When we visited the Unseen Colour exhibition at Lacock, we were looking at an unexpected side of Werner Bischof. Famous for his stark black-and-white photojournalism, Bischof also experimented with a pioneering colour process: the tricolour separation camera.

The Tricolour Camera in Action

Before Kodachrome and other colour films became practical in the 1930s, photographers used ingenious methods to capture colour. The tricolour separation process worked like this:

1. Light enters the camera

A beam-splitting prism inside the camera divided the incoming light into three paths. Each path passed through a different filter: red, green, or blue.

2. Three negatives recorded at once

Each filtered light beam was projected onto a separate piece of black-and-white film. All three exposures were made simultaneously — a major advantage over earlier methods that required three exposures in sequence with filter changes (which caused colour fringing if anything moved).

3. Recombination

In printing (or, today, by scanning and aligning the negatives digitally), the three monochrome records could be recombined. When red, green, and blue layers were stacked, the result was a full-colour image.

Strengths and Challenges

✅ High Quality

Because each colour channel was captured on large, sharp film, the final prints could be strikingly detailed and vibrant.

❌ Bulky and Complex

The cameras were heavy, the prism system reduced light, and processing required careful alignment of three separate negatives.

❌ Practical Limits

Although simultaneous exposure avoided ghosting, in practice the size and complexity of the equipment meant subjects were often still lifes, staged portraits, or architecture rather than fast-moving street scenes.

Bischof’s Contribution

In the late 1940s, Werner Bischof embraced this demanding technology. The results, rediscovered and shown in Unseen Colour, are luminous and modern-looking. They show how adventurous he was, exploring colour long before it became mainstream in documentary photography.

Why It Matters Today

For us as photographers, the tricolour process is more than a historical curiosity:

It reminds us how colour once required experimental tools and patience.
It shows how technical limits shaped creative choices.
And it links directly to modern digital practice: when we split or recombine RGB channels in Photoshop or Lightroom, we are echoing a technique pioneered more than a century ago.

Werner Bischof: Unseen Colour and the Tricolour Camera