Early two-color process (ca. 1920–1950)—red and green mixed onto black-and-white negative stock. Creates warm or cool color casts without true color—nostalgic, technically limited.
Biochrome works differently than one might think today — it's not true color film, but an optical illusion based on black-and-white negative material. The process uses two color separations (red and green) exposed onto the same black-and-white stock. The result: a monochrome-looking film with subtle color casts, which are more akin to tinting than true color. From the 1920s to the early 1950s, this was a practical solution — cheaper than Technicolor, more space-saving, but aesthetically very limited.
On set, you notice it immediately: Biochrome material reacts strangely to certain light wavelengths. Red and green tones are preferentially captured, everything else falls off into grayscale. A blue jacket looks dark gray, a red curtain appears brownish-orange — not through filtering, but through the two-color architecture of the negative. This leads to a warm or cool mood, depending on which color dominates. You can partially control this with lighting, but you don't have real control — the material's limitations are hard and unforgiving.
Practitioners used Biochrome as a budget option back then — for B-movies, short films, sometimes even feature films with smaller budgets. The limitation became an aesthetic signature: the color film always looked slightly artificial, somehow nostalgic, even before anyone had uttered the word nostalgia. In editing, Biochrome gives you little room for color correction — what you've captured is what you've got. Bleaching and fading effects occur naturally because the material is less stable than more modern color processes.
Today, Biochrome primarily interests restorers and film historians. The material stocks have become fragile, and the chemical processes for new production have long been discontinued. When working with old material in archives that was produced using this method, you recognize it by the characteristic color cast and grain — and by the fact that you don't have color separation like with true color negative. This is important for digitization: Biochrome material requires different scan profiles than Technicolor or modern color negative.