The Lippmann process is an early colour photographic technique invented by Professor Gabriel Lippmann (1845–1921). In this process, light passes through a nearly transparent emulsion layer and is reflected back by a layer of mercury. The interference between the reflected and incident light forms a latent image in the emulsion, which can initially be processed in black and white. When viewed against a reflective backing, the image reveals its original colours.
Understanding the Lippmann process is important for historians and photography enthusiasts studying the evolution of colour photography. Although it was never commercially widespread due to its complexity, the technique demonstrated the physical principles of colour reproduction and paved the way for future advances in colour imaging and photographic science.