Early color photography required exposures through red, green, and blue filters. The three single-color images were combined, the strengths and interactions of RGB blended into one multicolor image. This "trichrome" technique is still a popular method of capturing infrared light.
The physicist Gabriel Lippmann took a different approach. He was inspired by the phenomenon of light interference, where the phase differences in light waves result in variations of amplitude and intensity. The result is a brilliant spectrum of possible colors:
Many species have evolved to exhibit phase interference - the iridescence of a beetle's carapace or a peacock's feathers is the result of the very same phenomenon that enabled Lippman to create color images in a single exposure.
Lippmann's interference photographs were termed "photography in natural colours by direct exposure in the camera;" a novelty then that now describes practically every color photo.
The result of Lippman's photographic process was a positive image (like slide film) rather than a negative. However, Lippmann plates appear colorless until white light hits them at a certain angle; this light illuminates the interference structure of the photograph, replicating the light shining upon the scene when the exposure was taken. The dark room and single point of illumination you see below is ideal for their viewing.
Later, Lippmann's interference photography technique was expanded with the use of lasers and 3D (rather than 2D) emulsion to create holograms, which capture their subject's light refractions at a variety of angles. White light holograms are viewable under the same conditions as Lippmann's photographs: by shining white light upon them at an angle to illuminate their interference patterns.
