Miyoshi Ayama

Color appearance in the entire visual field: color zone map based on the unique hue component

To provide the fundamental data for a color zone map, the color appearances of nearly unique hue stimuli presented over the entire visual field were qualitatively and quantitatively evaluated by hue and saturation judgments, blackness evaluation, and categorical color naming. The hue of red and green stimuli shifts toward a unique yellow, while that of yellow and blue does not change with an increase in eccentricity. The saturation of all the stimuli falls with an increase in the eccentricity in all directions. On the basis of the unique hue component, color zone maps for red, dark yellow, yellow, green, and blue stimuli are drawn. All the color zone maps extend over a wider region in the temporal and lower directions than in the nasal and upper directions of the visual field. The results are compared with the color zones of previous studies. The relationship between the color zones and the color categorization, as well as the underlying mechanisms of reduced saturation and hue shift, is discussed.

Brightness-to-luminance ratio of colored light in the entire chromaticity diagram

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 increases. However, the results of the other two observers showed very low B/L ratios, especially in the reddish region. The B/L ratios based on each observers sensation luminance were also calculated. Although the contour lines of equal B/L ratio become less atypical for the latter two observers, they still showed low B/L values compared to typical results. Large individual differences of the B/L ratio in the whole area of the chromaticity diagram were indicated.

Adaptation luminance simulation for CIE mesopic photometry system implementation

A simulation method to determine adaptation luminance is proposed for implementation of the CIE mesopic photometry system. The simulation takes four factors into account: luminance distribution, eye movement of observers, surrounding luminance effect and area of measurement. Each factor is modelled as a two-dimensional geometrical function. The method determines an adaptation luminance for the area of measurement through four calculation steps. The simulation method was applied to examples of luminance distributions of outdoor lit scenes and the results were compared with possible simple predictors of adaptation luminance. The comparisons suggest that the average luminance of the area of measurement can be considered as a good approximation in most of the cases. Exceptions are scenes for pedestrians in which there are many bright sources surrounding the area of measurement.

Color appearance in peripheral vision

This paper will present a literature survey on the basic aspects of the possibilities for color presentation in the peripheral visual field and the results from some experiments from two laboratories in Japan and in Sweden. The method used was a color naming technique that included hue and saturation/chromaticness estimations of color stimuli of different eccentricity. In one laboratory, the size effect was also examined. Unique hue components of the stimuli were derived from the results of hue and saturation/chromaticness estimates. The results from the two laboratories showed similar tendency despite the differences in the experiments. The results showed that an increase of the retinal temporal eccentricity to 40 deg caused impaired color appearance especially for red and green colors. Smaller color stimuli, subtending 2 deg of visual angle, were perceived as less chromatic as larger color stimuli, subtending 6.5 deg of visual angle. The results are in line with some earlier studies showing that blue and yellow colors are better perceived than green and red in periphery.

Effects of visual and conversation tasks upon a functional visual field while driving

Effects of visual task and/or conversation task on functional visual field (FVF) during driving was studied experimentally. Red or pink circular target was briefly presented somewhere on a movie scene from drivers view in a car following situation, and the observers task was to indicate the target position. The visual task loaded on the observer was to read out the two alphabet letters presented in the center of the visual field. The conversation task was to answer an easy question orally. The FVF narrowed with the visual task as well as with the conversation task, while it markedly shrinked when both visual and conversation task were imposed simultaneously.

Influence of surround luminance upon perceived blackness

In this study, we investigated how the luminance ratio of the surround field (Ls) to that of the central field (Lc) influence the perceived blackness of the central field in a simple configuration of concentric circle (Experiment 1) and in digital images of masterpieces (Experiment 2). Results of Experiment 1 showed that perceived blackness of the central field becomes more blackish and deeper as the contrast between Lc and Ls increases. Results of Experiment 2 showed that perceived blackness of black area surrounded by relatively bright area in artistic images is stronger than the perceived blackness given by the same luminance contrast between the center and surround in a concentric circular configuration.

Quantitative evaluation of color appearance between different media and appearance modes

In this study, we examined the influences of color media and mode of appearance on color appearance by evaluating four attributes of color such as saturation, hue, blackness, and categorical color. CRT display and color charts were used as color stimuli both were presented in the surface-color mode as well as in the aperture-color mode. Results indicated that saturation, blackness, and categorical color names strongly depend on the mode of appearance, while the results of hue does not clearly show such a tendency.

Whiteness perception in Japanese and Finnish under cool and warm fluorescent lamps

In this study, we conducted the experiment to compare the whiteness perception of Finnish and Japanese observers. The rank order of perceived whiteness among seven nearly white Munsell chips (Value is 9.25 or 9.5, Chroma is 0, 0.5 or 1.0) under the fluorescent lamps of correlated color temperatures of 3000K, 5000K, and 6700K was determined. Observing condition employed in the two laboratories was exactly the same as well as the experimental procedure. In 3000K condition, the results of Japanese and Finnish observers agreed with each other quite well, while as the correlated color temperature becomes higher, the results from the two laboratories showed different tendencies. Negative correlation was found between the whiteness rank order and the metric chroma for all of the results.

Online Shopping and Individual Consumer Adaptation: The Relationship Between Fabric-Identification Ability and Prior Knowledge

This chapter describes the adaptation of individual consumers with regard to shopping for clothes online. Consumers who shop online are sometimes disappointed if the textural and tactile properties of purchased clothing differ from their expectations. However, some observers can determine cloth quality quite well from an image. Understanding how such observers identify fabric is critical for developing a technology for presenting cloth information that is adaptable for each observer. To accomplish this, we performed a fabric-identification experiment in which we asked 18 observers to distinguish pieces of cloth through blind tactile perception while viewing cloth images on a display. We also conducted a questionnaire survey to quantify each observer’s knowledge of fabrics, experience, and interest by using polar questions and visual analog scales (VASs). From these results, the relationship between fabric-identification ability and prior knowledge was investigated for each observer.

An examination of a gradation number for high-gradation displays based on luminance-differences

With recent advances in high dynamic range displays, high-gradation displays have been actively studied. High-gradation displays have more than 256 gradations. When a luminance range of a display is very wide, a luminance-difference between each pixel value becomes small by increasing a gradation number. If this luminance-difference is larger than just noticeable difference (JND), the viewer may see contours on changes in gradation. Therefore, the number of gradations must be set up so that the luminance-difference between each pixel value is smaller than JND [Toshiyuki et al. 2008]. On the other hand, in usual high-gradation studies [Seetzen et al. 2004], the number of recognizable gradations is treated as one of the performance metrics because medical use high-gradation displays are based on DICOM GSDF and have recognizable gradations. Therefore, we must examine what kind of luminance-difference is appropriate for the outside of the medical field because high-gradation displays will be used there as well.