It's been 150 years since Scottish Physicist James Clerk Maxwell showed off the world's first color photograph at a Royal Institution lecture in London. His discovery is incredible but, technically, it shouldn't have worked.
Best known for formulating classical electromagnetic theory and demonstrating that electricity, magnetism and light are all permeutations of the electromagnetic field, James Clerk Maxwell's research in optics led him to hypothesize the three-color method in 1855. The three-color method is based around the three types of color-sensing cones in the human eye: red, green or blue. Maxwell figured that the human eye could be fooled into seeing a full color picture if three slides of the appropriate color in the proper porportions were overlaid.
To demonstrate this effect, he and his assistant created the composite picture of the tartan ribbon you see above from three monochrome images, each filtered for a specific color. The only problem was that the emulsion that he used to capture the monochrome images was really only reactive to blue light. The green light emulsion barely registered anything outside the blue-green spectrum and the red light emulstion did nothing at all. So how did he end up getting a full-color image? Turns out the ferric thiocyanate he used as the red filter allows a large amount of ultraviolet light to pass through and red-dyed fabrics tend to reflect ultraviolet light as well as red. The red color he produced was not from the visual spectrum at all, instead he created a full color image from the ultraviolet, blue-green, blue spectrums.
Maxwell succeeded in creating the world's first durable color photograph — but for the wrong reasons. So happy birthday Color Photography, you're one of our favorite accidents.