CATHODE-RAY-TUBE TO REFLECTION-PRINT MATCHING UNDER MIXED CHROMATIC ADAPTATION USING RLAB

Color-appearance models are used to relate chromatic stimuli viewed un der one set of viewing and illuminating conditions to a differing set such that when each stimulus is viewed in its respective conditions, t he stimuli match in color appearance. These models assume the observer has a steady-state adaptation to each condition. In practice, observe rs often view stimuli ender mixed adaptation; this could occur when vi ewing CRT and reflection-print stimuli simultaneously. A visual experi ment was performed to determine whether the RLAB color-appearance mode l could be used successfully to generate reflection prints that match the appearance of the CRT when viewed under mixed states of adaptation and in turn as stand-alone images viewed under a single state of adap tation. Sixteen observers viewed four pictorial images displayed on a D-65, balanced CRT display in a room lit with cool-white fluorescent l uminaries. The RLAB color-appearance model was used to calculate corre sponding images where the observer's state of chromatic adaptation was assumed to be one of the following: adaptation to each device conditi on, a single adaptation at the midpoint of the two device conditions, adaptation to the CRT condition and a print adaptation shifted 25% tow ard the CRT condition, adaptation to the print condition and a CRT ada ptation shifted 25% toward the print condition, and a CRT condition sh ifted 25% toward the print conditionand a print condition shifted 25% toward the CRT condition. Each condition was compared pairwise and Thu rstone's law of comparative judgments was used to calculate interval s cales of quality. Observers first judged the reflection prints adjacen t to the CRT display selecting the image closest in color appearance t o the CRT image; they also categorized the closest image as ''acceptab le,'' ''marginally acceptable,'' or ''not acceptable.'' The images wer e again scaled except the display was turned off; this determined the best stand alone color reproduction. The observers determined that ima ges generated where it was assumed that the CRT adaptation was shifted 25% toward the print condition and a print adaptation was shifted 25% toward the CRT condition produced both the closest match to the CRT d isplay and the best stand-alone image. The mixed-adaptation matches we re acceptable or marginally acceptable on average 84% of the time. Thi s adaptational condition produced the most preferred stand-alone image s due to shifts toward regions of known preferred color reproduction.