Color Map Cycling: Impressions of Sunstone

by Sonya Shannon on August 29, 2010

Toronto, 1982

Long before Photoshop or even the now-extinct Quantel Paintbox, I had a wonderful two-dimensional painting tool box in the form of Paint, written by Alvy Ray Smith at the New York Institute of Technology on Long Island.

The image became radioactive, rippling through a bath of toxic hues…

In those days, color was still a major hurdle. The Paint software, which ran on a DEC PDP11-23 computer, used what were known as color maps or CLUTs—Color Look-Up-Tables. The color maps amounted to a digital paint-by-numbers approach to graphics, where the entire image at its maximum could only have 256 colors – far more than a box of colored pencil crayons, but nevertheless a razor-thin sliver of the whole visible spectrum.* In some ways the limited color space produced limited image quality, especially in large gradated areas. I remember blue, a favorite color of TV news identifications, smeared in ragged waves as it deepened from royal to midnight.  The effect was made worse because the room was permanently dark, the only light coming from old cathode-ray-tube monitors. It felt frustrating not to be able to smooth out the jagged color bands with something – a finger-smudge, some turpentine, water…but we were dealing with colored light and the idea of a dimmer or fader was far beyond the primitive on-off capabilities of the time.

Still, 256 colors had a wonderful capability because the color map could be animated – the entire palette could be rotated through each pixel of the image. The composition stayed still, while the colors cycled wildly through it! The effect was as if the image became radioactive, rippling through a bath of toxic hues that sometimes made it appear like a photographic negative, a drug-induced neon billboard, an entire movie made from a single picture. Perhaps the best example of this technique is the sequence in Ed Emshwiller’s early masterpiece, “Sunstone,” where the sculpted face changes mood, expression, and meaning thanks to the color map cycle. Even though we have gained so many new effects, I still miss color map cycling. In my mind it has taken on that era-defining retro-preciousness, and is to copmuter graphics what Agfa film is to photography or Technicolor is to movies.

*We have this limited-color phenomenon today with GIF and PNG images for the web. One way to reduce image size is to compress the number of colors into a fixed-size palette, such as 256.

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