Apparent Lightness Influenced by the Size of the Recognized Visual Space of Illumination

概要

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It is hypothesized that the apparent lightness of an object is determined relative to the size of the Recognized Visual Space of Illumination (RVSI), which is constructed in the human brain for an illuminated space, The apparent lightness of test patch was matched with that of a reference patch; they were respectively located in a test room and a reference room, which were both illuminated at 600lx. Two kinds of reference patches were employed, with N4.0 and N6.0 respectively. When the size of the RVSI of the test room was made smaller than the reference room by furnishing the walls, floor, and furniture in the test room with lower lightness of N1.5 compared to the reference room, the test patch with lowered lightness by about N0.5 in the case of N4.0 and about N0.7 in the case of N6.0 matched the reference patch, showing that the lightness in the test room was evaluated as higher because of the smaller size of the RVSI of the test room, thus confirming the hypothesis of the lightness recognition. When the RVSI was enlarged by furnishing the furniture in the test room with chromatic surfaces in addition to increasing the lightness by N1.5, although without changing the wall or the floor, the matching point shifted toward a higher lightness of the test patch as expected and excluding the description for the lowered lightness of the test patch with the simultaneous contrast.
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