Thesis (M.Sc.)--Chulalongkorn University, 2002

The human visual system normally treats the color from Cathode-Ray-Tube (CRT) displays as an attribute of light itself (light source color mode). By gradually decreasing the CRT luminance, the color onthe CRT begins to appear more like an object placed in the room. This is because the luminance of the CRT becomes so low that the color appearance on the CRT goes inside the border of the Recognized Visual Space of Illumination (RVSI), which represents the limit of the object color mode. The experiment was conducted to investigate the border luminance of 47 colors. The colors were chosen to cover the monitor color gamut. These colors were displayed on a CRT monitor under two different illuminance levels, 5 lx and 50 lx. The CRT monitor was carefully calibrated using the linear regression method and the transformation matrix between u'v' and RGB was obtained. Using this matrix, u'v' of color stimuli was converted into RGB code value for the display. The task of observers was to set the luminance of color stimuli at the border between object and light source color mode. The border was found to be high in colors that have chromaticity-coordinates close to that of the illumination in the observer's room. More saturated colors had lower border luminance. The borders at observer's room illuminance of 5 lx were lower than those at 50 lx. The result implies that the color displays on CRT monitor can change their appearance depending on the illumination condition of the room. In addition, the result was shown that the brightness of stimuli works as the dominant factor to determine the border of RVSI