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Chiba Vision Meeting 第98回千葉視覚研究会 特別企画


Seminar on
Color Vision & Shitsukan Perception
色覚と質感セミナー

色覚、質感研究分野で活躍されている新進気鋭の研究者である Durham大学のMaria OlkkonenさんとHelsinki大学のToni Saarelaさんの特別講演、 また、Nevada大学Reno校・Webster研究室大学院生のIvana Ilicさんと 千葉大学教員3名の講演による最新研究紹介を通して、 色覚や質感についてディスカッションする場にしたいと考えています。 年始のお忙しい時期かと存じますが、ぜひご参加いただければ幸いです。

Poster is HERE


Date & Place


Date: January 5, 2018 (Fri) 11:10 – 16:10
Place: Chiba University, Engineering Research Building 2 Conference Room  
(千葉大学西千葉キャンパス工学系総合研究棟2 2階コンファレンスルーム)

千葉大学 西千葉キャンパスマップ
(工学系総合研究棟2は、工学部(青のエリア)の11番の建物の隣、10階建ての建物です。)
http://www.chiba-u.ac.jp/campus_map/nishichiba/index.html

大学へのアクセス
http://www.chiba-u.ac.jp/access/nishichiba/


※ 参加申込不要・参加費無料

Program

11:10 - 11:15 Opening

11:15 - 12:00 Maria Olkkonen (Dept. of Psychology, Durham Univ.)
Is it green or blue? How memory and learning shape color perception

13:00 - 13:45 Toni Saarela (Dept. of Psychology, Univ. of Helsinki)
Surface material discrimination and cue integration

14:00 - 14:25 Ivana Ilic (Dept. of Psychology, Univ. of Nevada, Reno)
Contrast adaptation and artificial lighting

14:30 - 14:55 Eiji Kimura (Faculty of Letters, Chiba Univ.)
Biased averaging of colors in multicolored textures

15:00 - 15:25 Midori Tanaka (Collage of Liberal Arts & Sciences, Chiba Univ.)
A shitsukan reproduction approach on display device

15:30 - 15:55 Yoko Mizokami (Graduate School of Engineering, Chiba Univ.) Shitsukan perception influenced by the diffuseness of lighting

15:55 - 16:10 General Discussion & Closing

Abstract


Maria Olkkonen (Dept. of Psychology, Durham Univ.)
Is it green or blue? How memory and learning shape color perception

Both long-term and short-term experience with object color affects color perception. Memory colors (typical colors of familiar objects such as fruit) draw perceived color towards them, but colors can also be biased toward a recently learned average color, an effect called the central tendency bias (CTB). We have only recently begun to understand the parameters of such sensory learning processes. In this talk, we will address several fundamental aspects in the learning of color priors, such as the effect of noise on prior weighting; the time course of learning; and the learning of priors for different objects. Our results generally show that memory biases of perceived color develop rapidly and can be shape-dependent. Finally, we will discuss the relationship between shape-dependent color adaptation and learning.

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Toni Saarela (Dept. of Psychology, Univ. of Helsinki)
Surface material discrimination and cue integration

Surfaces and materials in our environment differ from each other in several ways: color, lightness, roughness, gloss, texture, and so forth. When discriminating materials, our visual system can potentially perform better by integrating information from several such visual "cues". In real-world settings, however, an observer might be uncertain about which cues are most informative at a given moment. We report experiments on the integration of color and glossiness cues in material discrimination under manipulations of extrinsic uncertainty. The stimuli were spectrally rendered images of 3D shapes. We independently varied diffuse and specular reflectance to produce a two-dimensional stimulus space, with stimulus color varying from blueish to greenish and specularity from matte to glossy. On each trial of the experiment, the observer compared a reference and a test stimulus, which in different conditions differed from each other in color, gloss, or both. The observer identified the bluer/glossier stimulus, and we estimated the discrimination threshold for each condition. We ran this discrimination experiment using two designs. First, in the no-uncertainty (blocked) design, the relative strength of the color and glossiness cues remained constant throughout a block of trials. In this case, the observer can set their decision criterion optimally for each condition. Second, in the uncertainty (mixed) design, all relative cue strengths were intermixed. The observer now does not know the particular combination of color and glossiness in advance and is thus forced to "monitor" both cues. Observers performed better with two cues compared to individual cues. Performance overall was better in the no-uncertainty experiment, especially in the case of single cues. We next fit a cue-integration model based on signal-detection theory to the data. The model assumed independent processing and statistically optimal integration of the two cues and took the effect of extrinsic uncertainty into account. The model gave a good fit to the both no-uncertainty and uncertainty experiments. The human system can integrate color and glossiness cues to improve the discrimination of surface materials. When extrinsic uncertainty increases, performance suffers, but only as much as would be expected by the change in the task structure.

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Ivana Ilic (Dept. of Psychology, Univ. of Nevada, Reno)
Contrast adaptation and artificial lighting
Ivana Ilic, Lorne Whitehead, Michael A. Webster


Contrast adaptation and artificial lighting Ivana Ilic, Lorne Whitehead, Michael A. Webster Artificial illuminants vary not only in their mean chromaticity but also in the range of colors they produce. For example, new high-gamut LED illuminants can expand the saturation of reds and greens by ~30%. We explored how the visual system might adapt to changes in the color distributions under different illuminants. A set of simulated surfaces (Munsell spectra) was constructed to form a uniform circle of chromaticities in cone-opponent space, when illuminated by a Planckian radiator with a color temperature of 2724 or 4000 K. Corresponding sets were then calculated for the same surfaces under a 3-primary LED spectrum with the same mean chromaticity. Observers simultaneously adapted for 3 minutes to a random sequence of the same surfaces under each pair of Planckian vs. LED sources, shown in two 4-deg fields above and below fixation. A new color was sampled from the distributions every 200 ms. Test stimuli were then shown for 500 ms in the two fields and interleaved with 4 sec of re-adaptation. The tests included 16 chromaticities uniformly sampling different chromatic angles relative to the illuminant mean. The test pair were yoked so that increasing the test contrast in the top field reduced it in the bottom field or vice versa, and observers adjusted them to match their appearance. Matches to an unadapted field showed that both illuminants induced strong contrast adaptation. However, matches between illuminants required significantly higher contrast along the reddish-greenish axis for the LED adaptation, consistent with a sensitivity loss induced by adaptation to the higher red-green contrast created by the LED spectra. Our results suggest that commonly available light sources may significantly alter the states of contrast adaptation in the visual system, and that this contrast adaptation is important for understanding the perceptual consequences of both short and long-term exposure to different illuminants. Funding: EY-10834

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Eiji Kimura (Faculty of Letters, Chiba Univ.)
Biased averaging of colors in multicolored textures

As natural objects in everyday situations generally consist of multicolored surfaces, efficiently extracting the mean of the surface color distribution should be critical for object recognition and material perception. In fact, when a multicolored texture is presented, we can easily extract its mean color. However, a bias of the perceptual mean toward the most saturated color has been reported. Our study confirmed that the bias is mostly limited to the dimension of saturation (hue averaging was very precise). Moreover, the results showed that the bias depended on the variance, rather than the range, of element colors and that color averaging relies on cone-opponent representation. We will discuss a possibility that highly weighting the most-saturated element colors can be a good heuristic for surface color perception, as the highest contrast regions can be highly informative about surface reflectance.

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Midori Tanaka (Collage of Liberal Arts & Sciences, Chiba Univ.)
A shitsukan reproduction approach on display device

Recent imaging technologies such as color management, HDR imaging and high-resolution display devices have been realizing realistic and precise image reproduction of HDR scenes among different color-imaging devices with true-colors. However, by using these current imaging technologies, it is still difficult to accurately represent the shitsukan (perceptual appearance) of real-world objects on such display devices. Can we feel the equivalent shitsukan obtained from physically faithful displayed images with real objects? To face up to this question, firstly, I explain our results of psychophysical experiments that investigated the perceived shitsukan difference between the real objects and reproduced images displayed on a monitor. Next, as a faithful shitsukan reproduction approach on a display device, I introduce our image processing algorithm based on the human's pupil behavior during a careful observation of object surface.

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Yoko Mizokami (Graduate School of Engineering, Chiba Univ.)
Shitsukan perception influenced by the diffuseness of lighting

The diffuseness of lighting could influence the appearance of various surface properties, and it would be important to investigate them systematically. We examine how the surface appearance of test samples with different roughness and shape changed by diffused light and direct light using real samples in real miniature rooms. We prepared plane gray test samples with different levels of surface roughness with matt and gloss surfaces. A sample was placed in the center of a miniature room with either directed light or diffused light. The appearance (e.g. glossiness, naturalness, roughness) of test samples under diffused light were evaluated in comparison with that under the direct light, which was served as a reference. The color appearance of colored test samples was also evaluated by choosing corresponding colors from a Munsell color chart placed in a separate viewing box. The results showed that samples tended to appear less glossy and smother under diffused light than direct light, and their difference was larger for a sample with rough surface. On the other hand, color appearance was barely changed, implying stable color perception among different lighting conditions.


Sponsor & Support

共催:
千葉視覚研究会

グローバルプロミネント研究基幹リーディング研究育成プログラム   
質感イメージングの創成~情動モニタリングを用いた良質な質感評価ビッグデータ   の集積と質感認知に基づいた高度質感イメージング技術の産業応用~

グローバルプロミネント研究基幹リーディング研究育成プログラム   
多元的認知行動解析に基づく心理特性の解明とその応用

Supported by: Initiative for Realizing Diversity in the Research Environment
文部科学省科学技術人材育成費補助事業 ダイバーシティ研究環境実現イニシアティブ(連携型)