In modern society, elderly people tend to become enthusiastic users of displays. These displays are optimized for the visual properties of young adults ignoring the specific attributes of the vision of the elderly though the existence of differences is evident. It is true, however, that most of the investigations follow a bottomup paradigm (changes of optical density, neural changes, etc.), and their results are too ambiguous to be taken into account directly in display optimization for the elderly, partly because there is a long-term adaptation, which apparently recompensates for some of the changes in the human visual system. Preference is a high-level psychological factor having a very important impact on the acceptability of color displays. The present article follows a top-down methodology to investigate these age-related differences directly. The first part concentrates on functionalities of the human visual system: white point preference, chroma perception, unique, and preferred hues. Results confirm the long-term compensation theory for the elderly observers along with the chromatic content decrease of perceived colors. The second part investigates preference differences in case of photorealistic images in terms of global and local contrast, white point, average chroma, and the effect of several image color manipulation techniques. Results indicate significant differences between young and aged observers' color image preference, some of which can be explained with neuro-physiological changes, others may be attributed to cultural implications.

In this article, the color appearance of a large (858) homogeneous self-luminous visual stimulus was studied in a psychophysical experiment. Large stimuli were displayed on a plasma display panal (PDP) monitor. The large stimuli were viewed with a fixed viewing time (2 s). They were compared with 28 and 108 stimuli presented on a grey background on a CRT monitor. The socalled ''color size effect'' was found to be significant. The color stimulus was perceived to be lighter when it was large compared with the 28 and 108 situation. But we did not find the general increase of chroma claimed in previous literature. We found only small hue changes. A model of the color appearance of large-field stimuli is presented in terms of the CIELAB L*, a*, and b* values of the corresponding 28 and 108 stimuli.

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Design principles are formulated to develop visually optimal multiprimary subpixel architectures. Two new hexagonal subpixel architectures optimized for multiprimary color displays are shown, each designed according to these principles. These new multiprimary pixel architectures are considered to be useful to eliminate the color fringe artifact. They are expected to yield images of better visual quality than previous three primary color architectures including the RGB stripe architecture. A new image rendering method is also formulated for multiprimary subpixel architectures. This method can be used with and without subpixel rendering. An error function is defined enabling proper chromaticity reproduction and enhanced luminance resolution.

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