This study was conducted to evaluate the effects of wall and floor lightness on the perception of interior space under lighting from the ceiling surface. A series of psychological experiments were conducted to evaluate the four spatial parameters: magnitude values of volume, width, depth and height of interior space, using a one-tenth scale model of a room measuring 2.4 m in height and 4.5 m in width and depth. A luminous ceiling comprising a 2 mm polystyrene paper that transmitted light was included to maintain uniform interior illuminance. LED lamps were installed above the polystyrene paper. The average vertical illuminance level was approximately 60 lx. This experiment was conducted to compare results from the standard model with those from comparison model. The comparison model consisted of base and assort colours which means that one of surfaces (sidewall, opposed wall or floor) was painted in a colour different from other surfaces. The four achromatic colours used in this experiment were N9.5, N8, N6 and N3. A magnitude estimation method was applied to evaluate the four spatial parameters. The twenty subjects (15 women and 5 men) were asked to look into each model in turns through a viewing aperture in the rear wall and to compare the four spatial parameters of the comparison model with that of the standard model. The results can be summarized as follows.
· The higher the base colour and assort colour lightness, the higher was the perception of the interior space.
· As for the magnitude value of volume, when the lightness of base colour was higher than that of the assort colour, the magnitude value of the volume decreased. However, if floor was painted with an assort colour, this effect was blurred. On the other hand, when the lightness of the base colour was lower than one of the assort colour, the magnitude value of volume became increased. However, if the opposed wall painted with the assort colour, this effect was enhanced.
On comparison with previous studies, these results turn out to be similar. However, there were a few differences in floor colour lightness effect. For example, the effect of extend to the model for the upper by floor colour lightness can't found, and floor colour lightness has significant in only magnitude value of depth.