Color Matching by Analog Computing Around 1960

comic computer cutoutI just read an article from IEEE Annals of Computing history about the COMIC Color-Matching Analog computer built and sold by Davidson and Hemmendinger, a US firm. It seems the computer is pretty well known inside the colorant industry, actually, and it provides an interesting example of how to do a good-enough solution to break open the market – while leaving the user in control of the process to build faith in the approach.

Basically, what the COMIC did was to help users create mixes of dyes to match an existing color. COMIC means COlorant MIxing Computer. This is a much more difficult problem than it might sound like- especially when different types of light (daylight, fluorescent, classic light bulb, etc.) and different types of materials have to be taken into account. The COMIC helped solve this by letting a user virtually try different combinations and strengths of dyes and virtually see how well they matched an existing color setup – within its limitations, such as not being able to handle matching across different materials. The background science was already known and expressed as a set of linear equations, and the COMIC implemented these computations in hardware so that the user did not have to do it by hand. The computation was performed using analog circuits , controlled by many potentiometers that users would turn to provide parameters and input values. The result was shown as set of dots on an oscilloscope, where the user strove to bring all dots down to the zero line (which was often not actually possible to do, but I guess a close match was often good enough).

The business case for the machine that cost 10000 USD or more in 1960 was that you could work much faster when creating a new blend of colorants to achieve a certain hue – anecdotes indicate that you could reduce the number of actual physical test dye runs by half or more using the COMIC. In many ways, this feels like a typical MVP solution – useful enough to get a job done, with known limitations, and quick to the market. It also laid the ground for later more sophisticated solutions. Quite interesting.

To do the job, profiles for each dye used had to be loaded, and each profile was a special electronic box that contained the parameters of a particular color in a custom box. Today, it is just a few values in memory, but for the COMIC it was a physical box that was physically loaded into the machine. Beautiful and concrete, but also pretty expensive and hard to scale up.

As you would expect, the work of the COMIC was overtaken towards the late 1960s by digital machines, as they came down in price and the computations needed could be performed quickly enough at a price-point that could match the analog machine. A key point of the COMIC when it was launched was actually that it cost much less than the digital machines of the same time. At that particular point in time, for this particular application, being special-purpose was actually cheaper than being general-purpose. That happens from time to time in all markets.

I also see indications that the COMIC worked as an educational tool. The dyer working with the machine had to detect quite a bit of skill, and this seems to have made the whole process easier to accept than a more black-box machine. By letting the existing professionals into the loop, it would appear that it helped introduce the idea of machine-assisted and computation-based color matching to the industry. It might have been more difficult to go straight to a fully-automated much more capable solution – there is sometimes virtue in being primitive and require manual intervention when a new technology is being introduced. I believe that it is easier to teach people to accept a “smart” solution if they see the internals first. Once trust is established by seeing it work, more and more automation and “magic” is acceptable.

I found a good description and a nice photo of the machine at the British Society of Dyers and Colourists (SDC), see http://colour.sdc.org.uk/2014/04/technicolour/.

The theory of color matching is described at http://www.rpdms.com/wineyrpt.html.

* Full citation: David Hemmendinger, “COMIC: An Analog Computer in the Colorant Industry”, IEEE Annals of the History of Computing, Volume 36, Issue 3, August 2014.

 

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