Abstract
The color of any object in a space is correctly perceived only when an observer correctly understands how the space is illuminated, or in our expression when he constructs a complete recognized visual space of illumination, RVSI for the space in his brain. For the construction of the RVSI the observer has to perceive a 3D space that is filled with illumination and he needs to see objects and others in the space which we call the initial visual information, IVI. It is our supposition that the most efficient IVI is planes to surround the space and the present paper investigates which planes are more efficient than others. A gray test patch was placed in an actual room illuminated at 60 lx by a ceiling light and a small area around the test patch was additionally illuminated by a white, red, yellow, green or blue spotlight that works as a hidden illumination. When the only test patch was illumianted by the hidden illumination the subject judged its color in relation to the main room illumination, namely as high lightness, or colorful, but when planes were inserted within the hidden illumiantion area he could now know the existence of the hidden illumination and judged the color of test patch more closely to its original gray color. For eight different combinations of the inserted planes, namely the back wall, the floor and/or the two sidewalls, the apparent color of the test patch was measured by the elementary color naming to investigate the efficiency of combinations. It was found that the four walls combination that enclosed the test patch was the most efficient IVI. Among three element planes the back wall was most efficient, the floor the next and the side walls the least.