Summary

The differences between paints, photographic dyes, phosphors and inks, the materials on which they are used, the differences in the lighting and viewing conditions, as well as the variations in the reproduction processes, make even an acceptable reproduction difficult. Colour Management Systems, CMSs, are computer programs. that often improve the translation of the colours of one medium, the input device, for example a Photo CD ROM, digital camera or scanner and photographic original, into the available colours of another medium, the output device, which may be a monitor, proofing or printing system. To do this, the CMS must have good information on the range of available colours of the original and the colour rendering errors of the input device, on the one hand, and the range of available colours of the output device on the other. This information is usually stored as a data set for each type of input and output device and called a colour profile. The CMS must also have algorithms that can transform the colours from the input into an acceptable representation on the output. In the case of newsprint and newsinks, this usually means compressing all colours of the original into a smaller palette of colours. The CMS should also allow the user to select the type of transformation to suit different objectives in the reproduction - which may vary from a pleasing reproduction with highly saturated colours, to mail order catalogue reproduction where close to exact calorimetric matching under a standard lighting condition is required. As long as a suitable colour profile is available, CMSs can take away much of the guesswork that is needed to set up colour tables for digital cameras or colour scanning systems. Colour transformations similar to those performed by highly-developed, high-end scanners can be achieved on far less expensive equipment. While most images need additional processing for cropping, sharpening and fine tuning of colours. the use of a good CMS provides a much better starting point for the image adjustment and generally improves the quality, cost-to-performance ratio and productivity of low and mid-range input devices. The Swiss graphic arts research institute, EMPA/UGRA, in St. Gallen, Switzerland was given the task of determining the requirements of a CMS and testing some of the systems against that criteria.