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The Hexachrome Hi-Fi colorant set has added Orange and Green to the normal Cyan, Magenta and Yellow inks used in the extant printing process. The new inks have been added to expand the gamut of printable colors. This new ink set maximizes the total volume of the printable gamut. Therefore, both lightness and chromaticity bounds were considered in the design of the new Hexachrome ink set. This method of adding extra inks is being explored by others to develop richer reds, greens and blues in other reproduction techniques. These new inking systems require new measurement standards to control ink density, dot gain and ink trap on press. Spectrophotometery is suggested as a new standard to control the complex interaction of these new ink combinations. The use of spectral tags is now possible because of the introduction of low cost spectrophotometers. These new instruments will allow inks to be completely described by their spectral signatures. The establishment of spectral signatures as the new standard instead of density will allow new inks to be used and controls to be specified without having to define yet another set of status filters. Tags are being employed to specify the targeted use of color images in a document. Recently the ability to add a PostScript colorant tag has been made possible with the ColorTron spectrometer and software developed by Light Source Computer Images. These colorant tags can be added to the image files to completely describe the preferred reproduction. These can indude the overprint ink spectra which better specify the interactions of the primary ink sets. The new specification should also include measurement conditions so that the control conditions can be accurately repeated at any location. The world of printing is no longer an isolated community where a single measurement instrument was used to control a press. In this production scenario, the repeatability of the instrument was more important than accuracy. With image files now being distributed widely over electronic networks , the need for accuracy, precision and known measurement method is becoming paramount in the control of printing dependent on the new extra-trinary processes.
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