Abstract Gamut volume is one of the parameters generally used for the characterization of printers and other imaging devices. However, it can also be used for monitoring color print fading. Relative gamut volume changes plotted as a function of the exposure dose can be conveniently used to determine the fading rate and corresponding lifetime. Calculation of the gamut volume is a challenge on its own, as a set of isolated points in three-dimensional space does not define a unique body in any obvious way. This problem has been addressed using the quick-hull algorithm combined with a non-linear convexing transformation of the measured data points and subsequent determination of the convex hull. In this article, the optimal degree of convexing is determined empirically on an extensive set of 19 samples including essentially all presently used photoprinting techniques. The actual use of gamut volume changes for monitoring of color print fading is illustrated on selected samples.
Abstract In many practical applications, printed images or text are exposed to a light source, making their lightfastness an important characteristic. Good lightfastness assures good color stability after prolonged use. In this study an accelerated aging procedure using a xenon arc lamp was applied to induce and investigate the degradation of Altona test chart color images and patches of offset and electrophotographic prints on papers made of virgin and 100% recycled fibers. In this article the authors present a new image processing method based on chrominance histogram quantification and discuss its applicability and performance with respect to the conventional spectrophotometric approach. The chrominance histogram quantification method using printed images proves to be a viable alternative to the established spectrophotometric measurements that are implemented on color patches and yield 2D color gamut information.