Access to graphic information is becoming more and more important for the Blind. This is due partly to developments in the workplace - particularly the necessity to use graphic user interfaces to software - and partly a result of the increased freedom to integrate into everyday life, education, and work - which involves comprehending information as diverse as town maps, pictorial signs, or technical drawings. Obviously, a need therefor exists to create useful graphic output for the Blind. It is not possible, however, to simply print a graphic on a tactile medium and expect the Blind to be able to use it. For one thing, while structures as small as 0.2 mm can be perceived tactually, the resolution at which the Blind can distinguish individual dots or features is typically about 2 mm. For another, neither perspective nor color information can be depicted one-to-one in a tactile image. Finally, the way the Blind extract information from a graphic differs substantially from visual perception. This is why certain procedures and informal standards have evolved for the representation of information, based on best practice on the one hand, and on available technology on the other hand. However, recent technology development significantly extends the possibilities for printing tactile graphics, so a reassessment may be helpful.
In general terms, "reduce to the max" (rttm) is the dogma of tactile graphics. This is especially important when discussing computer-controlled embossing, where raster images with a resolution of typically 10 or 20 dpi are printed. The possibilities for displaying abstract graphic information such as curves, dia-