Multiperspective understanding of cognitive behavior and its application (MUCB)
|13:15-14:00||Colour When the Light Changes
Prof. Brian Funt
(School of Computing Science, Simon Fraser University)
|14:05-14:50||Seeing with Variable Lighting
Prof. Sérgio Nascimento
(Centre of Physics, Campus de Gualtar, University of Minho, Portugal)
|15:00-15:45||Hue and Warm-Cool Feeling of Lighting Colors
Assoc. Prof. Youngshin Kwak
(School of Design and Human Engineering, Ulsan National Institute of Science and Technology)
|15:50-16:35||Colour Emotion for Interior Lighting
Prof. Li-Chen Ou
(Graduate Institute of Color and Illumination Technology, National Taiwan University of Science and Technology)
|16:45-17:25||Research activities in MUCB|
|Flexible Mean Brightness Judgment for Luminance Ensembles
Prof. Eiji Kimura and Yusuke Takano
|Spectral Lighting Technology for Realistic Appearance Reproduction
Assis. Prof. Keita Hirai
Color When the Light Changes
Prof. Brian Funt
The colour (i.e., RGB in the context of digital imaging) of an object depends very strongly on the light illuminating it. When the light is changed, the colours change. Work in the field of colour constancy tries to account for such changes; however, is it really possible to do so? In this talk, I will discuss two difficulties related to current approaches to this problem. The first difficulty relates to estimating the colour of the light. The vast majority of illumination-estimation methods assume there is only one source of light in a scene, but this assumption is almost always violated. What are the consequences of this? The second difficulty concerns metamer mismatching. Metamer mismatching refers to the fact that since many different surface reflectances can be metameric under a given light (i.e., yield identical RGB) the colour of an object under a second light is only constrained to lie within a volume of possible RGB values. Results using a recent algorithm for computing exact metamer mismatch volumes show that this volume is much larger than one might have guessed. What are implications of this for colour constancy? What also does meatier mismatching tell us about the color rendering properties of light sources?
Brian Funt is Professor of Computing Science at Simon Fraser University where he has been since 1980. He obtained his Ph.D. in Computer Science specializing in Artificial Intelligence from the University of British Columbia in 1976 followed by a post-doc at Stanford. His research focus is on computational approaches to modelling and understanding visual perception generally and color in particular. He serves on the board of the Colour Research Society of Canada and is a regular contributor to the CIC and AIC colour conferences. He has authored roughly 200 papers, the majority of which concern colour.
Seeing with Variable Lighting
Prof. Sérgio Nascimento
In our daily life we are exposed to a variety of light sources having very different spectral properties. Direct sun light at different times of the day or filtered by clouds, tungsten, fluorescent or LED lights, are all part of our modern visual environment and influence how the objects and complex scenes are perceived. Although our visual system has the property of color constancy, i.e., keeping the color appearance of objects even when they are illuminated by lights with different spectra, the process is not perfect and some residual color changes are perceived when the illumination changes. In this talk I review the variability of natural illumination and how the visual system deals with such variability. I will also review how the illumination affects the chromatic diversity perceived, how the quality of illumination can be estimated with quantitative indices and describe experiments to estimate the best illumination for specific settings, e.g. commercial counters and museum environments. It will be concluded that although daylight produces generally good visual quality, in some specific situations a less smooth spectrum may produce more pleasant visual impressions.
Sérgio Nascimento is an associate professor with aggregation of physics at Minho University, Portugal, where he teaches optics, vision sciences, and colour science. His research focuses on colorimetry and colour vision, in particular applications of spectral imaging, colour constancy and colour rendering, colour in art and models of colour vision. He is a member of the Board of Directors of the International Color Vision Society and topical editor for colour vision of the Journal of the Optical Society of America A.
Hue and Warm-Cool Feeling of Lighting Colors
Assoc. Prof. Youngshin Kwak
The hue and ‘warm-cool' feelings, in response to 48 test lighting colors, were investigated following adaptation to either 3500K or 5000K by twenty participants. The results showed that yellow-blue and ‘warm-cool’ feelings are closely located around the Planckian locus, while red-green roughly follows the line orthogonal to the Planckian locus in CIE u’v’ color space, at both 3500K and 5000K settings. The poor performance of the current color appearance model suggests the necessity of the color appearance model development for the lighting colors.
Youngshin Kwak is an Associate Professor at the School of Design and Human Engineering, Ulsan National Institute of Science and Technology (UNIST). She received her BSc (physics) and MSc (physics) degrees in 1995 and 1997 from Ewha Womans University, Seoul, South Korea. After completing her PhD studies at the Colour & Imaging Institute, University of Derby, UK, in July 2003, she worked for Samsung Electronics, South Korea. Since February 2009, she has been working as the professor at the School of Design and Human Engineering, Ulsan National Institute of Science and Technology (UNIST), South Korea. Her main research interests include human color perception, color emotion, visual appearance, and the quality of 2D and 3D images.
Colour Emotion For Interior Lighting
Prof. Li-Chen Ou
The relationship between colour and observer response in terms of semantic feelings, or the so-called “colour emotion” in the co-authors’ previous studies, has focused on colour patches or colour images as the stimuli, presented either in a viewing cabinet or on a calibrated computer display. Psychophysical findings have shown that such a relationship was consistent and predictable, and was culture-independent for some semantic scales. For instance, observer response for “active/passive” can be well predicted by a modified version of CIELAB difference between the colour stimulus and a medium grey. Little is known, however, as to whether these findings can also apply to interior lighting. LEDs have become a dominant light source and can easily manipulate light colours to create an atmosphere. Can a room lit by a coloured light create a specific feeling that is shared by individuals in the room? Can the relationship between light colour and the observer’s response be also consistent and predictable, just like what has been discovered in the conventional colour emotion studies?
To answer these questions, the present study used four Philips Color Blast RGB LED lamps to light an entire experimental room, 3.5m (width) by 2.5m (depth) by 2.3m (height) in size, decorated like a fashion store to provide a context. Thirty observers, 15 females and 15 males, all university students with normal colour vision, participated in the experiment. The observers were seated individually in the middle of the room and were asked to evaluate the room and their emotional state in terms of 4 scales “liking”, “brightness”, “tension” and “dizziness”. This was followed by rating of the observer’s own facial skin using a mirror in the room in terms of 5 semantic scales “like/dislike”, “smooth/rough”, “natural/unnatural”, “young/old” and “feminine/masculine”.
Each observer was asked to rate the room and his/her facial skin using the 9 scales described above after the eyes fully adapted to the lighting condition, with adaptation time of 2 minutes. For the evaluation of the room, the observer was asked to focus on the wall right before him/her when rating the room but could look around to better appreciate the appearance of the room.
There were 40 light colours used in this study, consisting of 25 white lights and 15 coloured lights. All of the 40 light colours had the same luminance value, 300 cd/m2. The 25 white lights were selected to cover 5 Duv levels, -0.02, -0.01, 0, 0.01 and 0.02, and 5 CCTs, 3000K, 3500K, 4000K, 5000K and 6500K. The 15 coloured lights included 5 hue regions, red, yellow, green, blue and purple, and 3 levels of purity as defined by using Illuminant E as the reference white in the u’-v’ chromaticity diagram. The sequence of the 40 light colours was randomised for each observer.
The experimental results for white lights show that the Duv level had a strong impact on “brightness”. The white lights at negative Duv, i.e. those located below the Planckian locus, tended to feel brighter than those at positive Duv. Regarding “liking”, observers tended to like the room when Duv ≤ 0 more than when Duv > 0. The findings for “liking” were found to correlate well with “brightness”. The experimental results also show that facial skin tended to look young, smooth and feminine for negative Duv more than for positive Duv. Nevertheless, the “natural” response for facial skin was found highest for Duv = 0. The results also show strong influences of CCT on the observer response. The observers tended to feel less dizzy and feel the room was brighter when CCT = 5000K or 6500K, and they also found their facial skin more natural, younger and more masculine for high CCT. Nevertheless, the highest rating for “smoothness” of facial skin was found to be at 4000K. The above findings regarding white lights indicate that the room tended to feel brighter, more liked, less tense and less dizzy for Duv < 0 than for Duv > 0. This tendency was found more significant for high CCTs, i.e. observers tended to prefer white lights having negative Duv and high CCT (5000K and 6500K). For coloured lights, the experimental results show that blue and purple lights had the highest rating for “brightness”, while green and yellow lights had the lowest rating. Red and green lights were not preferred because they tended to create greater tension and dizziness. Among the 5 hue regions, yellow light was found to have the highest rating for “naturalness” for facial skin. Blue and green lights tended to make the facial skin feel old, rough and masculine, while red and purple lights tended to make it feel smooth and feminine. The purity of light colour had a strong influence on observer responses not only for feelings of the room but also for facial skin. The experimental results show that the higher the purity, the more tense and more dizzy the room tended to feel, and thus the room was less liked. The higher the purity, the less natural and less young the facial skin tended to appear, and thus was less liked. Based on these findings, predictive models were derived for some of the scales used in the study for the evaluation of colour emotion for interior lighting. The models are useful for general applications in interior lighting design.
Li-Chen Ou is a Professor at the Graduate Institute of Colour and Illumination Technology, National Taiwan University of Science and Technology, Taiwan. He has been the Division Secretary of CIE Division 1: Vision and Colour since 2015 and the Chair of CIE technical committee TC1-86 “Models of colour emotion and harmony” since 2011. Dr. Ou received a B.Eng. from National Cheng Kung University, Taiwan in 1995, an M.A. from National Chiao Tung University, Taiwan in 1997, and a Ph.D. from the Colour and Imaging Institute, University of Derby, UK in 2004. His areas of interest include colour science, colour psychology and lighting design.