Scottish physicist James Clerk Maxwell demonstrated to London's Royal Institution a technique for producing color images by combining three separately filtered photographs -- a method that would underpin color photography, television, and digital displays for the next century and a half.
Maxwell's demonstration used a tartan ribbon as its subject, fittingly Scottish. He had photographer Thomas Sutton take three separate black-and-white photographs of the ribbon through red, green, and blue color filters, then projected all three images simultaneously through matching filters onto a screen, superimposing them to recreate a full-color picture.
The underlying insight came from Maxwell's theoretical work on how the human eye perceives color through three types of receptors, a theory he had been developing for years. The photographic demonstration proved the theory could work in physical practice, even though the emulsions of the era were not very sensitive to red light, making the ribbon experiment's colors somewhat muted and inaccurate.
Maxwell himself is far better known for his equations unifying electricity, magnetism, and light -- arguably the single greatest achievement of 19th-century physics, later called by Einstein the most significant event since Newton. But this color photography demonstration was a rare instance of a great theorist also personally pulling off a hands-on technical feat, one whose descendants include every RGB pixel on every screen in the world today.
Key people: James Clerk Maxwell, Thomas Sutton