Journal Papers
（準員）溝上陽子、（専門会員）池田光男、（会員）篠田博之
(Associate Member) Yoko Mizokami, (Fellow Member) Mitsuo Ikeda
and (Member) Hiroyuki Shinoda
立命館大学
Ritsumeikan University
It is hypothesized that the apparent lightness of an object is determined relative to the size of Recognized Visual Space of Illumination (RVSI), which is constructed in the human brain for an illuminated space. The apparent lightness of a 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 600 lx. 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.
KEYWORDS: recognized visual space of illumination, lightness, brightness, lightness constancy
[full paper: PDF(1,302KB)]
Mitsuo Ikeda, Hiroyuki Shinoda and Yoko Mizokami
Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577 Japan
We hypothesized that the recognized visual space of illumination (RVSI) was constructed in our brain when we grasped the state of illumination of a space. The importance about the RVSI is that it is three dimensional and is valid not only at the surfaces of the existing objects in the space, but also for the entire portion in the space where no objects exist. With this property of RVSI we are able to predict the appearance of an object surface in terms of lightness as well as of color when the object shifts from one place to the other in the space. The three dimensionality of the RVSI is proved by giving a hidden illumination within a space and by asking a subject to judge the lightness or color of a test patch placed in the area of the hidden illumination. In spite of the additional light on the test patch the subject did not recognize that the light was added but simply felt that the surface was made of a higher lightness or colored by transferring the light into an increase of the reflectance factor of the test patch. The results can be interpreted if we assume that a same RVSI exists throughout the entire space including the area of the hidden illumination.
Key words: illumination, lightness, apparent lightness, color constancy, color mode
[full paper: PDF(1,133KB)]
Yoko MIZOKAMI, Mitsuo IKEDA and Hiroyuki SHINODA
Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577 Japan (Received May 25, 1998; Accepted July 22, 1998)
According to the concept of the recognized visual space of illumination (RVSI) the lightness of an object surface is perceived in relation to its conceptualized size. To prove this proposition the lightness of gray test patches was judged when they were located at various positions inside an illuminated space composed of two rooms in the depth direction from a subject. No retinal image arrangement was changed in the test patch and its immediate surroundings, but the front room had walls, floors and furniture lower in lightness by the amount of N1.5 than the back room to make the RVSI of the former smaller despite the illuminance in the entire space being the same. The results showed that the apparent lightness of the patches was perceived higher by amount of about 13 in L* units for the N4 test patch and about 20 for N6 when the patches were located in the front room, in accordance with the prediction. It was stressed that the experiment of lightness judgment should be conducted in a three dimensional space rather than two dimensional plane as done by several investigators.
Key words: lightness, apparent lightness, illumination, recognized visual space of illumination.
[full paper: PDF(801KB)]
Mitsuo IKEDA, Hiroyuki SHINODA and Yoko MIZOKAMI
Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577 Japan
Many experimental results have been reported which demonstrated deviation of the apparent lightness from the calculated lightness based on spectral reflectance, and these have caused debate among researchers as to the models to explain them. The judgement of lightness of objects that we see in the outside world is one of the most important tasks in our daily life. We proposed the recognized visual space of illumination, RVSI, as a three dimensional recognition constructed in the brain for the outside world, and showed that the apparent lightness was determined in relation to the size of the RVSI. In the present paper the concept was applied to various results of lightness experiments such as the White effect and simultaneous contrast, and based on the proposition that an observer first builds a three dimensional RVSI from a two dimensional pattern and the lightness of a test patch was judged in relation to the size of this RVSI, the results were then globally and nicely explained. A new demonstration of a pattern was proposed to give different apparent lightness for patches with the same physical lightness to strengthen the proposition. The importance of distinguishing between a test patch and a surrounding field was emphasized when one does a lightness experiment and interprets the results.
Key words: lightness, apparent lightness, lightness consistency, illumination, color consistency, recognized visual space of illumination
[full paper: PDF(1,755KB)]
（準員）溝上陽子、（専門会員）池田光男、（会員）篠田博之
(Associate Member) Yoko Mizokami, (Fellow Member) Mitsuo Ikeda
and (Member) Hiroyuki Shinoda
立命館大学
Ritsumeikan University
The size of the recognized visual space of illumination (RVSI) is a concept for expressing the perception of brightness of a space recognized by an observer. If he/she recognizes the space as being brightly illuminated, the size of RVSI is said to be large. The apparent lightness of an object placed in the space is determined relative to the size of the RVSI. The size is controlled by changing the illumination level of the space. It can also be controlled by changing the lightness of the interior of the space even if the illumination is kept constant. Then the apparent lightness of the object becomes lower with an interior having high lightness. Two miniature rooms in the depth direction from a subject, were illuminated at the same illuminance level, but the front room had walls, floors and furniture with lower lightness than the back room. It was expected that the RVSI of the front room would be smaller in size than that of the back room. The two rooms were separated by a partition frame projecting from the side walls. In this paper the effect of the projection size of the partition on the size change of RVSI at the boundary of the two rooms was investigated by measuring the apparent lightness of a test patch along the depth of the rooms for three different projection sizes. It was found that the effect of projection size was not significant and the separation into two RVSIs was mainly achieved by interior lightness.
Keywords: lightness, apparent lightness, brightness, illumination, recognized visual space of illumination
Yoko MIZOKAMI, Mitsuo IKEDA and Hiroyuki SHINODA
Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577 Japan
It was shown that the color property of the recognized visual space of illumination, RVSI was controlled by changing the initial visual information by arranging objects in the room all shifting toward orange direction. We constructed two miniature rooms, D and I, both illuminated by the same daylight type fluorescent lamps but arranged with furniture of different color, those in room I shifting toward color as if they were illuminated by an incandescent lamp. Subjects felt as if room I were illuminated by an incandescent lamp. A test patch was placed midair in each room and its color was judged. When the test patches were placed in room I their colors were all perceived to be shifted toward greenish blue compared to those of test patches placed in room D, in spite of having the same illumination. The results imply that the apparent color of an object is determined not by its chromaticity, but in relation to the color property of the RVSI of the room where the object is observed.
Keywords: color, color appearance, color constancy, interior, illumination, recognized visual space of illumination, simultaneous color contrast
[Full paper: PDF(934KB)]
Mitsuo IKEDA, Yoko MIZOKAMI, Sachi NAKANE and Hiroyuki SHINODA
Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577 Japan
(Received September 25, 2001; Accepted February 12, 2002)Whenever we enter a space illuminated differently from a previous space whether in color or in illuminance, we can quickly adapt to the new atmosphere and can again perceive white for the originally white object; this is known as color constancy. This phenomenon is explained by rotation of the recognition axis of the recognized visual space of illumination (RVSI) toward the illumination color. The explanation then predicts that the color appearance of a test patch changes radically toward the opposite direction from the color of illumination when the physical property of the test patch is kept unchanged at a neutral white. This prediction was confirmed by Experiment 1, where eight different colors of illumination were employed. The test patch appeared very vivid in color and shifted toward the opposite direction from the color of the illumination. In RVSI theory the light source color mode is explained by the release of the test patch from the restriction of RVSI. The release can be achieved by increasing the luminance of the test patch and the color appearance of the patch should then return to its own color as it is no longer controlled by RVSI. In Experiment 2 these predictions were investigated by increasing the luminance of the test patch to a much higher level than that of the objects in the lit room fixed at an illuminance of about 100 lx. The color appearance of the test patch indeed became the light source color and returned to the original neutral white. Emphasis was given in the course of the experiments that the subjects were observing the test patch presented in a real 3D space where the subjects also stayed inside so that they could properly construct RVSI for the space.
Key words: color appearance, color appearance mode, object color, light source color, recognized visual space of illumination, illumination, elementary color naming method
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