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Computer Systems

The images of the series Color Grids – most of them in the Herbert W. Franke Collection in the Kunsthalle Bremen today – were created with the so-called Sicograph, a device developed in 1973 by the Siemens company in Erlangen for medical use. It was one of the first sicographs with which X-ray images could be converted into color and optimized thanks to digital image evaluation, and finally printed out in color.

However, no X-ray image was used for the input, but rather the image of a random pattern, which first had to be read into the system via a punch card. This random pattern could then be alienated using various image processing processes, including the smoothing of contours, the grouping of representative points into fields, or the reduction of colors. The changes could be followed in real time on a monitor. The output device was a precursor of today’s inkjet plotters, with which liquid colors could be applied from cartridges to paper. The ink liquid was forced through nozzles and emerged in the form of fine jets whose intensity was modulated by high voltage. The paper sheet was stretched over a rotating drum, which the nozzle attachment scanned in 90 seconds, dot by dot and line by line. The special color mood was created because the plotter could only work with the three basic colors red, green, blue, but had no black color cartridge.

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