Mitsuo Ikeda

Rajamangala University of Technology · Thailand Institute of Fashion Research

This study aimed to demonstrate and quantify the greenish-blue color of veins using tissue paper and stocking via the simultaneous color contrast phenomenon. The colors of real skin and veins were accurately measured in the experiment and used as a reference to simulate the color of the skin and the veins. Subcutaneous veins were simulated using gr...

In this study, simultaneous brightness contrast was investigated using three different devices: 2D (paper), 3D (space), and D‐up. The paper stimuli were made by printing papers, the space stimuli were produced by illumination in a two‐rooms experimental booth, and the D‐up stimuli were shown to subjects using a D‐up viewer. The brightness of test p...

Our previous experiment showed that the color appearance of color chips changes depending on the color of illumination. In this article, we continued to analyze the previous data of 23 color chips under six vivid colored illuminations (red, yellow, green, cyan, blue, and magenta) that were assessed by 100 subjects. We found that there were usually...

Nowadays, a light system has been changed from fluorescent to LEDs with lots of benefits, especially generating various color lights. However, not much research has studied the color appearance of objects under vivid LEDs. In this research, twenty-six color chips were randomly seen under thirteen colored illuminations composed of six hues like red,...

The ability to stably perceive the color appearance of objects under various colored lights is called color constancy. Color Constancy Index (CCI) is a measure to quantify the efficacy of the phenomena. This index was commonly calculated based on a color space that used a physical color object as a reference. It varies from 0 to 1 to show poor colo...

Many kinds of research have been undertaken on color constancy under various illuminations; however, not many people have studied this domain in the context of vivid colored light. In this article, 23 color chips were assessed using the elementary color-naming method under 13 RGB-LED illuminations of six hues as red, yellow, green, cyan, blue, and...

The experiment was done by using two-room technique to create two demonstrations of simultaneous color contrast. In both cases the quanta catch was made equal at the central retina of 13° x 10°. A small gray patch was placed in the center of the colored paper, while the other case, the same area was stimulated by LED illumination to have the same c...

This is an experiment on the simultaneous color contrast done by two techniques. In both cases the quantal catch was made equal at the central retina of 13°×10°. In one technique a small gray patch was placed on a colored paper, while in the other technique the same area was stimulated by the same color as for the paper technique but by illuminatio...

The color appearance of the afterimage of the simultaneous color contrast pattern was investigated by the elementary color naming method. The color appearances of the surrounding, an afterimage of the surrounding, and the test patch were measured, and the results were shown on the polar diagram of the opponent colors theory. The colors of both the...

It is said that we cannot have color constancy in a photograph. The concept of recognized visual space of illumination (RVSI) asserts that chromatic adaptation occurs when one perceives the illumination that is filling a space and not the objects in the space. It predicts then that if one perceives a 3D scene in a photograph, then color constancy w...

When we look, under daylight, at a scene in a photograph taken under an incandescent lamp, it appears very reddish, showing that color constancy is not maintained. According to the recognized visual space of illumination (RVSI) concept, color constancy should exist in a photograph if one can perceive three dimensions in it. This prediction was conf...

People get cataract in their eyes when they age. The color perceived by the senile cataract eyes desaturates because of the environment light that scatters in the eyes by the hazy crystalline lenses. We investigated the effect of the desaturation on brightness of objects in terms of the equivalent lightness L, which is composed of the achromatic li...

According to the recognized visual space of illumination concept, space perception is essential for color constancy. It should be possible to experience the color constancy in a picture if we perceive a three-dimensional space in the picture.A dimension-up (D-up) viewer was constructed to perceive a space for a picture. An experimental room illumin...

Communication window lighting (CWL) had been proposed as a system to provide information from the external world into a closed space. In this system, the brightness and color of the external world are reproduced on windows to provide information such as time, direction, and weather. In our experiment, subjects estimated the perceived time, directio...

The cataract eyes can be characterized by three elements; luminance, spectral distribution, and scatter, which are perceived as brightness, color, and fogginess, respectively. Change of any of the three elements may affect visual performance. The foggy element, which refers to the perception associated with a change in the optical scatter of the cr...

The visual perception of the cataract eyes is composed of three elements, color, brightness, and haze. The color element is related to the reduced transmittance of light at short wavelengths of crystalline lens, the brightness element to the reduced transmittance at entire region of wavelength, and the haze element to the opacity of the crystalline...

The theory of the recognized visual space of illumination (RVSI) is that the color appearance of objects in a space is determined in relation to its recognition axis RX whose direction is determined by the brain action to adapt to the illumination in the space. Thus the color constancy holds. RX is applicable to objects in the space but not to an o...

Color appearance was measured for a test patch which was placed in a test room illuminated by the daylight type of illumination and was looked at from the subject room illuminated by one of the four colored illuminations, red, yellow, green, and blue, through a window of three different sizes. When the window was the smallest so that only the test...

Previous study [Cunthasaksiri et al., Color Res Appl 2004;29:255–260] showed that simultaneous color contrast (SCC) of an achromatic center-chromatic surround configuration is a result of a cognitive process where color appearance of the center stimulus is determined in relation to a cortical representation of illuminant for a space or recognized v...

The border luminance of the test stimulus between the natural and unnatural object color, y yn B u was obtained for different spatial sizes of the immediate surround to prove that n B u can be determined based on a new recognized visual space of illumination (RVSI) that is assumed to be constructed for the immediate surround separately from the RVS...

The color appearance was measured for a test patch which was placed in a test room illuminated by daylight lamps and was looked at from a subject room illuminated by one of four colored illuminations, red, yellow, green and blue, through windows of various sizes. When the window was small so that only the test patch was seen within the window the c...

Understanding illumination is necessary for the perception of color and brightness in an object's surface. We call such understanding the recognized visual space of illumination, or RVSI. In particular, we use the term `brightness size' of RVSI to describe an observer's perception about the intensity of illumination. The brightness size of RVSI is...

Appearances of an object color in a space are determined by a cortical representation of illuminant for a space or the recognized visual space of illumination (RVSI). The simultaneous color contrast phenomenon on a simple center-surround configuration can be explained by RVSI. It is hypothesized that our visual system constructs an RVSI on the surr...

The color of an object placed in a room goes through various modes of color appearance if its luminance is increased independently from the room illumination; from the natural object color to an unnatural object color, and to the light source color having two borders. We were interested in investigating the determining factor for the first border a...

It is known that color constancy does not hold in a photograph. This could be because the photograph is recognized as a two-dimensional paper. Based on the concept of the recognized visual space of illumination (RVSI), it is predicted that color constancy holds in the photograph if it is perceived as a 3-D scene. We examined whether the color const...

The spatial characteristic of color assimilation with a grating was investigated in terms of the perceptual size. Strength of assimilation was assessed on color gratings at several vergence angles without changing the retinal size. The perceived size of the grating was also measured as a function of the vergence angle. Our results showed that the s...

Ten years have passed since we proposed a new concept called recognized visual space of illumination (RVSI). The central idea of the concept assumes that our brain first recognizes how a space is illuminated and then judges colors of anything seen in the space in relation to the RVSI constructed for the space. In another expression we say that the...

We have proposed a new estimation method for a perceived brightness of a room based on the concept of the recognized visual space of illumination, or RVSI. We use the term ‘brightness size’ of the RVSI to express an observer’s perception of the intensity of illumination. We define the border luminance between the surface color and the unnatural sur...

The retinal image of the outside world is two dimensional and the brain automatically transfers the 2D image to 3D space in order that a human can recognize the world correctly. A printed black and white picture of a grating or a cube was presented to subjects through a viewing box to exclude other objects than the pattern so that the brain was pro...

The apparent color of an object depends on how we recognize the space where it is placed in terms of illumination. We call this the recognized visual space of illumination (RVSI). What we see in the space first, namely, the initial visual information (IVI) determines properties of the RVSI, and we will show in this paper that the walls surrounding...

Color constancy is an important feature of the human visual system. Our visual system adapts almost instantly to new illumination and we can perceive the color of objects in a new space correctly whatever color the illumination may be. This feature is not solely that of a commercially available camera. The difference between the human visual system...

Understanding illumination is necessary for the perception of color and brightness in an object's surface. We call such understanding the recognized visual space of illumination, or RVSI. In particular, we use the term ‘brightness size’ of RVSI to describe an observer's perception about the intensity of illumination. The brightness size of RVSI is...

We recognize the outside world as a 3-D space in spite of its two-dimensional retinal image. We demonstrated a two- dimensional photograph could be perceived as a 3-D scene in a special 'dimension-up' viewing condition that a subject observed only the photograph. The color constancy was then realized in part even in the photograph and its degree in...

Based on the concept of the recognized visual space of illumination an experiment was conducted to measure the color appearance of a white test patch under the conditions where it was perceived as the object color and the light source color. The apparent color was measured by the elementary color naming method when it was viewed through a green col...

Understanding of illumination performs an important role in perceiving the color and brightness of object's surface. Especially, we can evaluate observer's perception about intensity of illumination by the concept of the brightness size of recognized visual space of illumination, RVSI. Our previous work showed that the RVSI size is determined by th...

We don't normally perceive the light source color in a night scene photograph even at the spot of a shining lamp, although of course we do perceive the color if we are in the corresponding real world. This different experience can be nicely explained by the concept of the recognized visual space of illumination, RVSI. We see the light source color...

We found an interesting phenomenon concerning the motion perception and the mode of color appearance. We suppose you are holding a stiff sheet of picture and move it laterally to and fro in front of the eye. Though the picture and all items in it move physically altogether with your hand, your perception is not always so. But when the picture that...

The purpose of the present research is to show that color contrast can be also achieved by manipulation of perceived size and to generalize the idea that perceived size is more fundamental to color contrast and assimilation than retinal size of images. In the experiment we assessed color appearance of grating for three color combinations with four...

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 illu...

It will provide us an effective method to study the color perception of the elderly if we can employ for young subjects a pair of glasses with color property chosen to simulate that of the elderly. One problem has to be solved before using such glasses based on the concept of the recognized visual space of illumination, that is, the size of the gla...

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 o...

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 furnitu...

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 o...

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...

Brightness-to-luminance (B/L) ratios based on the CIE 1924 V (λ) for 195 test stimuli equally sampled from the whole area of the CIE1976(u′, v′) chromaticity diagram were measured for four color normal observers. The results of two observers were similar to results in previous studies in that the B/L ratio increases as purity of the stimulus increa...

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 dire...

A series of our previous studies showed that we can experience a sense of continuity between two physically separated spaces by adjusting the illumination in them. In the present paper we measured the illuminance and color of the illumination that provided a sense of continuity between two rooms connected by a window. In the experiment the illumina...

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 obj...

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 a test patch was matched with that of a reference patch; they were respectively located in a test room and a...

Increasing (or decreasing) the convergence angle can shrink (or expand) the perceived size of an object without changing its retinal size. The present report deals with the question of whether such a change in perceived size affects visual acuity. We investigated the effects of perceived size on the legibility of letters, using a telestereoscope wh...

When a test patch is locally illuminated by, for example, a slide projector, so that its luminance is much higher than those of other objects in a scene illuminated with a main lighting source, the appearance of the patch is perceived as unnaturally bright and the situation is expressed as the appearance being out of the Recognized Visual Space of...

Continuity perception between two spaces can be obtained in general by adjusting the illuminance level of one of the spaces, when we say that the recognized visual spaces of illumination of the twospaces were made equal. This continuity can be experienced, for example, when an observer in a room looks outside through a window and the illuminance of...

Colored surfaces appear brighter than expected from their lightness and the discrepancy has been solved by replacing the lightness by the equivalent lightness defined by the brightness perception. The equivalent lightness increases with illuminance level under which the surfaces are observed. This concept was introduced based on the heterochromatic...

When an observer outside a room looks in through a window, s/he gains two Recognized Visual Spaces of Illumination, RVSIs, one for the room and the other for the outside where the observer stays. By adjusting the illuminance of the room the two RVSIs can be made equal and the observer perceives continuity between the two spaces, or in other words,...

A room beyond a window can be perceived continuously from an observer's room if the illuminance level of the latter rom is properly adjusted. This is achieved by equating the two RVSIs, or the recognized visual spaces of illumination, of the rooms and can be applied to the lighting of houses to enhance the amenity for residents. In designing the li...

One can immediately judge the state of illumination of a room by observing various objects in the room such as furniture and wall paper. The appearance of the objects, e.g., their color and brightness, constitutes the initial visual information about the room, and the recognized visual space of illumination, RVSI, of the room that the observer gain...

We conducted an experiment in which subjects observed a picture of a natural scene while the picture was displaced according to a subject’s saccades. The threshold displacement ratio (the length of picture displacement/the length of saccade) that allowed subjects to perceive the stable picture was measured. In experiment 1 the threshold ratio was m...

In a situation where an observer stays inside of a room and looks at the outdoor scene through an window, he obtains two recognized visual space of illumination (RVSI) for the respective spaces. These two RVSIs differ normally as the illumination situation differs between the two spaces. It is possible, however, to equate them by controlling the il...

Two studies were conducted to investigate changes which take place in the visual information processing of novel stimuli as they become familiar. Japanese writing characters (Hiragana and Kanji) which were unfamiliar to two native English speaking subjects were presented using a moving window technique to restrict their visual fields. Study time fo...

A color matching task was done by one subject repeatedly to study color discriminability as a function of inter stimulus interval (ISI) in successive stimuli presentation. Reference and matching stimuli were presented alternately with a certain ISI (0-1000 msec.) The subject adjusted the color of the matching stimulus to match the color of the refe...

The behavior of gaze in the task of color matching was studied at various stimuli separations from 6 to 120 deg. for two subjects. Eye and head positions were measured with a limbus tracker and a CCD camera attached to a pair of spectacles. Whereas the time required per match was almost constant, the number of gaze shifts decreased and the fixation...

The empirical formulas introduced in our previous paper to calculate the equivalent lightness of colored surfaces when their Munsell color notations were known had a problem with the contribution of hue to the chromatic lightness particularly in the region of hue 5Y. We present a new formula for hue coefficient h (φ). The revised formula for equiva...

We examined the tolerance of full-field illuminance changes to perceive constant illumination on the picture across saccades. In the experiment, subjects observed a picture of an actual scene, while the illuminance on the picture was alternated between E and E-ΔE whenever subjects made saccades. The subjects reported whether they noticed any change...

In everyday life, we are often required to shift our gaze by a large angle by rotating our head to compare colors of objects which are considerably separated from each other. To assess the ability to discriminate colors under such conditions, the repeatability of color matching was studied as a function of stimuli separation. Color matching ellipso...

Although lightness is an important attribute of a colored object, it fails to express the brightness of the object and the object normally appears brighter than a gray scale even though the two are equated in lightness.The notion of the equivalent lightness was introduced to deal with the problem.Experiments have been carried out to measure the equ...

The study was made for structure of categorized color space in the aperture and the surface color modes. The color appearances of two modes were reproduced on a CRT display with or without a surround configuration. Subjects made categorical color naming with 11 basic color terms. The (x,y,L) color space divided with these terms showed structural di...

Principal component analysis was applied to spectral luminous efficiencies determined by the heterochromatic brightness matching by 51 and 70 observers for the field size. 2° and 10°, respectively, which were used to derive the CIE Vb,2(Λ) and Vb,10(Λ). Four principal components were found to explain the individual variation. the two deviation indi...

Equivalent lightness was determined for 26 colored surfaces by heterochromatic brightness matching with a grey scale. The illuminance for observation was varied from 0.01 to 1000 lx to cover scotopic, mesopic, and photopic vision, and the equivalent lightness-versus-log illuminance curve was obtained for every stimulus. The shape of the curves did...

A text was replaced with a visual mask for a fixed duration every time the reader made a saccade. The threshold duration was measured when the mask was presented at the beginning of a saccade or a fixation, or at a certain delay after the onset of a fixation. The effect of the mask on reading time, as well as on the subjective legibility of the tex...

Conspicuity of color changes according to illuminance because of the Purkinje shift. This makes it difficult to design safety clothes with a single color which gives always high conspicuity at any illuminance. To overcome the difficulty the combination of two colors, one being very conspicuous at day time and the other at night time, was proposed t...

Equivalent lightness of four colored objects, blue, green, yellow, and red, was obtained for illuminance levels covering the range 0.01 to 1000 lx by brightness matching to a grey scale. Three field sizes, 20', 1° and 6° arc of visual angle, were investigated. With the smallest size, for which no rod response was expected, the equivalent lightness...

The red, green, yellow, and blue curve portions of chromatic valence functions (CVFs) were measured by an iso-cancellation technique using three or four different chromatic standards (cancellation stimuli of fixed intensity and chromaticity) for each of the four curve portions. Curve shapes of the red, green, and yellow CVF portions varied with dif...

Spectral luminous efficiency functions were obtained by direct heterochromatic brightness matching for four different stimulus durations: namely, 10-ms, 200-ms, 1-s, and continuous presentation. The functions clearly changed in their shape, depending on the stimulus duration for two of three subjects. They showed usual double peaks at about 540 and...

Because of the Purkinje shift of human visual system, the conspicuity of colored cloth radically changes depending upon the illuminance level for the observation. A red cloth, for example, is very conspicuous at a day time, but it becomes almost black and unseen at dark night. By contrast, a light blue cloth goes the other way around and becomes ve...

Additivity of heterochromatic brightness matching was investigated between unique-green and red (660 nm), and between unique-blue and unique-yellow with 2-deg bipartite field composed of a 100 td white reference field and a bichromatic mixture field. Ten subjects participated in the measurements and the results showed wide varieties among subjects....

An empirical formula was derived to express the results of conspicuity of colors determined experimentally in the previous report with 12 different colored charts observed at illuminance levels covering the range from 0. dl to 1000 lx. The formula is in principle based on the CIE 1976 L*a*b*color space and the theoretical conspicuity was defined as...

Conspicuities of 12 colored charts were measured at six illuminance levels covering photopic, mesopic and scotopic regions. Grey background of six different values was used. An experimental method was used in which subjects picked up the charts one after another according to the conspicuity. The most clear change in the conspicuity was found for th...

Wavelength-discrimination thresholds were measured with stimulus durations of 8, 500, and 2000 msec for test wavelengths of 420 to 630 nm at equal luminance of 100 Td. With the short duration of 8 msec, the discrimination thresholds increased for most wavelengths, but they decreased for the wavelengths near 460 nm. This short-duration wavelength-di...

Brightness luminous-efficiency functions for point sources and for 2° and 10° fields are based on 6, 63, and 76 subjects, respectively. The function for point sources can be approximated by Judd’s 1951 modification of the CIE V(λ) function. The 2° and 10° functions differ greatly from V(λ). The two functions differ from each other only at wavelengt...

Detection probabilities for wavelength changes were measured as functions of stimulus onset asynchrony (SOA) with the chromatic double-pulse method. Two test stimuli of a wavelength λt were successively exchanged with a reference stimulus of a wavelength λr in equal luminance for a short duration with a SOA. Durations were 5 and 50 msec, and the SO...