Kodak last week announced that it was discontinuing its venerable Kodachrome film, sending it gently into that good night after 74 long years. Like Polaroid's discontinuation last year of all instant films, Kodachrome's demise makes it the latest victim in the transition from chemical, film-based photography to digital sensors, Photoshop, and archival inkjet printers. Though it may seem like an anachronism that has lived far past its prime, the oldest color film was a mind-blowing revolution when it was first introduced in 1935.

I don't mean to suggest that color photography didn't exist before Kodachrome—not by a long shot. The first known color photographs were taken in 1861 by James Clerk Maxwell. Maxwell's process, the foundation upon which later commercial processes were developed in the early 1900s, involved exposing three plates, each filtered by red, green, or blue. The resulting plates could then be projected simultaneously using the same red, green and blue filters, creating what was at the time the most accurate reproduction of color available. Photographic plates in those days weren't fully sensitive to the full visible spectrum, so this method wasn't fully exploited until the photographic documentation of Russia by Sergey Mikhaylovich Prokudin-Gorsky between 1909 and 1918.

A comparison of Bayer-pattern red-green-blue filters to Autochrome's orange-green-purple mosaic.

Later processes, including Joly Color, Autochrome, and Dufaycolor used a similar filtering process but included mosaics or other patterns of filters on the photographic plates themselves. These processes are in fact quite similar to the Bayer filtering used on the sensors in modern digital cameras. Like all silver salt-based films, digital sensors don't actually record color, but light intensity.

In the early 1900s, black and white film was filtered to achieve reasonably accurate color reproduction. In the 2000s, we do the same thing with digital sensors; however, we have the added advantage of digital interpolation—which attempts to fill in missing color data for each individual pixel position—something that wasn't available 100 years ago.

Even Technicolor introduced a color process as early as 1922 for motion pictures. The early Technicolor processes relied on bulky cameras that split light using a prism, filtering one side with red and the other with green. Each was then exposed onto separate rolls of film. Red and green prints were made and cemented together to create a "color" film. Technicolor later refined the process, adding a blue layer to the process for vibrant, "true" color and creating a process to create prints on a single layer of film—giving us results that we remember from The Wizard of Oz. Separating and filtering the light this way is still done for high-end, 3-CCD digital video cameras (remember, sensors—like film—are only sensitive to the intensity of light).

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. That company has committed to processing remaining stocks of Kodachrome—which Kodak suggests could be available until autumn of this year—until the end of 2010.

This haunting image of a young Afghan refugee was shot in 1985 using Kodachrome film.

Despite the benefits of digital photography, though, some photographers mourn the loss of the iconic film, famously praised for its color reproduction by none other than Paul Simon is his 1973 hit "Kodachrome."

Kodachrome was universally admired for its color reproduction, smooth tonal range, and excellent dark storage properties, which made it practically archival. Arguably the most famous image ever made on Kodachrome was a 1985 National Geographic cover shot by photojournalist Steve McCurry that featured a young Afghan girl. National Geographic relied on Kodachrome so heavily, in fact, that it ordered a custom batch of an ISO 200 version of Kodachrome when Kodak discontinued it earlier this decade. Though a majority of working pros shoot primarily with digital now, some have likened the loss of Kodachrome to a painter who could no longer get his oft-used brand of brushes or his favorite paints.

While we continue to march away from film to a day when all images will be captured digitally, it's worth recognizing that the technology that made Kodachrome possible gave us a world full of color images for a respectable 74 years.

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