I’ve always thought that Kodachrome slides have a particular colour profile, but I’m no expert. Can you tell me a little about them?
You’re absolutely correct. I’m not an optics engineer, but I can try to explain this. Kodachrome’s distinct colours have to do with its sensitivity to visible light.
Unlike anything else, it is basically a triple-layered, black-and-white film. Unlike most other colour films, the dyes are not part of the film and are only added once it’s processed at the lab. This required a lot of space, a complicated contraption of a machine, and chemistry specialists to monitor the several chemicals used for processing. This made for a very complicated process which cannot be done in a typical darkroom, an it is basically why no one can process it anymore. In the 1990s, Kodak developed
a computer-based “K-Lab” Kodachrome processing machine that could fit in drugstore photo labs, but they wrote off that idea soon after and destroyed most of the machines.
When Kodak started selling Kodachrome cine movie film (on 15 April 1935), it was one of the first (and the most feasible way) to reproduce true colour imaging, to do so with some stability and consistency, and to also be commercially viable to sell for consumer use.
Each of the three layers, like the cones in our eyes, is sensitized to different areas of the spectrum. This is trichromatism — or “three colours.” For us, our cones our optimized for red, yellowish green, and a deep blue (p. 22 on this PDF), while our brain combines these three signals into a single, coherent image. For Kodachrome, it’s more red, gold, and blue (or more specifically, their reversal analogues of cyan, magenta, and greenish-yellow before the complementary dyes are added), but still a lot like the way the human eye sees.
The “cyan” layer was apparently a challenge for Kodak’s engineers to reproduce accurately, so they made it disproportionately more sensitive relative to the other layers. This is why Kodachrome reds look like nothing else. When developed through the reversal chemistry, which includes adding each dye one stage at a time, it results in the striking reds, blues, and yellows. And because skin tones are principally brown (a combo of red, yellow, and blue), people also look really good when exposed correctly.
Also, unlike any other film or digital medium, Kodachrome has another unique quality: amazing texture and dimension. This is due to “edge acutance” (or “edge sharpness”), which happens when the three layers are stacked atop one another. When you look at the emulsion side of a Kodachrome slide, some of the film is visibly thicker in dark areas (if you ever had a 3D Viewmaster growing up and saw those ridges on one side of the film disc, it’s because they always used Kodachrome).
When you look at the slide on screen or when scanned, the variable thickness of these layers makes the edges of subjects appear to pop out relative to their background. It’s an optical illusion, but comparatively it almost feels like you can reach out and touch it.
[This also makes scanning Kodachrome really difficult, because scanners aren’t sure what to do with it, and it also goes back to why the colours don’t fade: because dyes are added later, the layers soak up only what the image has on it, whereas other films have all unused dyes which, over time, can start to change colour and cause fading. The sensors on most scanners are designed for this kind of film, not Kodachrome. This is why so many improperly scanned slides on Flickr come out looking so bluish.]
Kodachrome was never technically accurate for reproducing an unbiased colour spectrum, and it was why Kodak regarded it as an ancient film given the technical accuracy they achieved with later colour products. There’s one problem with this rationale: a digital camera or Velvia film might be more accurate, but that’s not necessarily how the brain sees the world. Being engineers, though, Kodak didn’t really consider that the Kodachrome palette is, for photographers, an aesthetic, subjective medium the way that painting with oil differs from other means.
But Kodak never really marketed that quality (much less promoted it at all after about 1992), and its loss of popularity after the 1980s came in part because so few people knew it was still being made until recently. If anything, teh internets (ethersphere, whatever) gave Kodachrome its one last breath of life from a new generation of photographers and filmmakers wanting to try it out — like this:
It is alleged to be the last music video ever made with Kodachrome, ca. September 2010.
Unrelated: this is another excellent music video example of Kodachrome from 1988:
More to follow.