Lovely Ars Technica piece reminding us that Kodachrome was a huge technical advance when it first appeared.
What Kodak did when it introduced Kodachrome in 1935 seemed nothing short of a miracle. The film had three separate light-sensitive emulsions, each filtered by the film itself to be sensitive to red, green, and blue light. During the complicated development process, these layers were developed and reversed, then coupled to dyes to create a full color transparency. Photographers and cinematographers of all types could use standard cameras, expose the film once, and get back a full color image. It should be noted that Foveon uses a similar concept for its X3, multi-layered digital image sensors today.
We take for granted this ‘single shot on a single piece of film’ ability today, since the multilayered, dye-coupler approach is the basis for all later color transparency and negative films. The main difference is that the dye couplers are included in the film emulsions themselves, greatly simplifying the development process—currently E-6 for color slides and C-41 for color negatives. The complicated, expensive, and environmentally challenging K-14 process for Kodachrome is a big part of the reason the film waned in popularity after the 1980s. In fact, only one lab in the country still processes the film—Dwayne’s Photo Service in Parson, Kansas.
LATER: Boyd Harris sent me a link to this fascinating site which contains a remarkable gallery of old 4×5 Kodachrome images. They make one realise what an extraordinary advance the film represented when it burst onto the scene.