Modelling incomplete chromatic adaptation on a display under different ambient illuminations

2019 ◽  
Vol 2019 (1) ◽  
pp. 231-236
Author(s):  
Rui Peng ◽  
Ming Ronnier Luo ◽  
Mingkai Cao
Keyword(s):  
Lower Degree ◽  
Chromatic Adaptation ◽  
White Background ◽  
Color Stimulus ◽  
Lighting Condition ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Illuminance Level ◽  
Adaptation Factor

The purposes of this study was to investigate the chromatic adaptation and adaptive whites on a display under various ambient lighting conditions with different chromaticity and illuminance. An image including black text and white background was rendered by means of the CAT02 chromatic adaptation transform, into 42 different white stimuli varying at 6 CCTs and 7 Duv levels. Twenty observers assessed the neutral white evaluations of each color stimulus via psychophysical experiments. The optimization based on the neutral white stimulus under each ambient lighting condition suggested a lower degree of chromatic adaptation under the conditions with a lower CCT and a lower illuminance level. The results were used to model the adaptive display white and the incomplete adaptation factor (D) for CAT02 under different ambient illumiantions.

scholarly journals Preferred skin tones reproduction of three ethnic groups under different ambient lighting conditions

2020 ◽  
Vol 2020 (28) ◽  
pp. 94-99
Author(s):  
Mingkai Cao ◽  
Ming Ronnier Luo ◽  
Guoxiang Liu
Keyword(s):  
Ethnic Groups ◽  
Large Scale ◽  
Skin Tone ◽  
Chromatic Adaptation ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Predicted Probability ◽  
Hue Angle ◽  
Scale Experiment ◽  
Facial Images

A large-scale experiment was conducted to investigate facial image quality on mobile phones. There were 8 original facial images from 4 skin tone types, each included a male and a female image. Each image was captured at 6500K and they were rendered to have 5 CCT (correlated colour temperature) and 5 Duv (the shifts away from the Blackbody locus) levels via CAT02 chromatic adaptation transform to simulate the effect of the images captured under 25 different lighting conditions. Each image was assessed under 9 ambient lighting conditions( including one dark condition) by 90 observers from 3 ethnic groups (Caucasian, Chinese and South Asian), each 30 observers. Preferred facial skin tone ellipse was established by maximizing the correlation coefficient between the model predicted probability and the preference percentage from the visual results. Four types of preferred skin tones had small differences in hue angle and chroma, but concentrated into a small colour region, about [24.7, 46.1°] for Cab* and hab values respectively. All ethnic group preferred images taken under illuminants having high CCT (6500-8000 K). It was also found that the chroma of the preferred skin tones will slightly increase as the ambient lighting CCT decrease.

Effect of Ambient Lighting on Frequency Dependence in Transcranial Electrical Stimulation-Induced Phosphenes

2021 ◽  
Author(s):  
Ian Evans ◽  
Stephen Palmisano ◽  
Rodney J. Croft
Keyword(s):  
Frequency Dependence ◽  
Quadratic Function ◽  
Linear Increase ◽  
Stimulation Frequency ◽  
Transcranial Electrical Stimulation ◽  
Lighting Condition ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Phosphene Threshold ◽  
Within Subjects

Abstract Inconsistencies have been found in the relationship between ambient lighting conditions and frequency-dependence in transcranial electric current stimulation (tECS) induced phosphenes. Using a within-subjects design across lighting condition (dark, mesopic [dim], photopic [bright]) and tECS stimulation frequency (10, 13, 16, 18, 20 Hz), this study determined phosphene detection thresholds in 24 subjects receiving tECS using an FPz-Cz montage. Minima phosphene thresholds were found at 16 Hz in mesopic, 10 Hz in dark and 20 Hz in photopic lighting conditions, with these thresholds being substantially lower for mesopic than both dark (60% reduction) and photopic (56% reduction), conditions. Further, whereas the phosphene threshold-stimulation frequency relation was linear in the dark (increasing with frequency) and photopic (decreasing with frequency) conditions, a quadratic function was found for the mesopic condition (where it followed the linear increase of the dark condition from 10-16 Hz, and the linear decrease of the photopic condition from 16-20 Hz). The results clearly demonstrate that ambient lighting is an important factor in the detection of tECS-induced phosphenes, and that mesopic conditions are most suitable for obtaining overall phosphene thresholds.

scholarly journals Human Centric Lighting: The impact of light on sleep and attention of factory shift workers

2020 ◽  
Vol 30 (Supplement_5) ◽  
Author(s):  
S Kindt ◽  
E Van de Putte ◽  
P Bracke ◽  
L Vandevivere ◽  
W Ryckaert
Keyword(s):  
Visual Comfort ◽  
Attention Task ◽  
Shift Workers ◽  
Lighting Condition ◽  
Lighting Conditions ◽  
Before And After ◽  
Illuminance Level ◽  
Sleep And Cognition ◽  
The Impact ◽  
Morning Shift

Abstract Introduction Increased blue-enriched morning light is often said to support circadian rhythm synchronization. Through a better sleep quality, one's cognitive and emotional functioning can also be enhanced. However, it is unclear which light characteristics (especially illuminance at eye level) are necessary to obtain a wellbeing effect in employees. This field study investigated different lighting conditions in a truck factory. Methods 71 shift workers participated in the study during their morning shift (6 am - 2 pm). Measurements of sleep (MotionWatch8), attention (D2 attention task, go no-go computer task) and visual comfort (questionnaire) were administered before and after changing the lighting conditions. A Human Centric Lighting-condition (HCL; vertical melanopic equivalent daylight illuminance (MEDI) = 250 lux, CCT=5000 K; N = 33) was compared with a control LED-condition (MEDI = 44 lux, CCT=4000K; N = 38). Results Results show that workers in the HCL-condition showed a larger improvement in sleep efficiency (p=.057) and concentration (p=.01) than the control LED-group. No differences were found in visual comfort between groups. Discussion Preliminary results are promising and show that 250 MEDI might be a sufficient cut-off to stimulate workers' sleep and cognition. The high illuminance level was not detrimental in the HCL condition for the perceived visual comfort. Key messages Blue-enriched morning light supports sleep and concentration in shift workers. High illuminance levels are not detrimental for the perceived visual comfort.

Real-world environment affects the color appearance of virtual stimuli produced by augmented reality

2019 ◽  
Vol 2019 (1) ◽  
pp. 237-242
Author(s):  
Siyuan Chen ◽  
Minchen Wei
Keyword(s):  
Augmented Reality ◽  
Real World ◽  
Mixed Reality ◽  
Rapid Development ◽  
Light Level ◽  
Color Appearance ◽  
Chromatic Adaptation ◽  
Lighting Condition ◽  
The Real ◽  
World Environment

Color appearance models have been extensively studied for characterizing and predicting the perceived color appearance of physical color stimuli under different viewing conditions. These stimuli are either surface colors reflecting illumination or self-luminous emitting radiations. With the rapid development of augmented reality (AR) and mixed reality (MR), it is critically important to understand how the color appearance of the objects that are produced by AR and MR are perceived, especially when these objects are overlaid on the real world. In this study, nine lighting conditions, with different correlated color temperature (CCT) levels and light levels, were created in a real-world environment. Under each lighting condition, human observers adjusted the color appearance of a virtual stimulus, which was overlaid on a real-world luminous environment, until it appeared the whitest. It was found that the CCT and light level of the real-world environment significantly affected the color appearance of the white stimulus, especially when the light level was high. Moreover, a lower degree of chromatic adaptation was found for viewing the virtual stimulus that was overlaid on the real world.

Flight By Periscope: Making Takeoffs and Landings; The Influence of Image Magnification, Practice, and Various Conditions of Flight

1966 ◽  
Vol 8 (1) ◽  
pp. 13-40 ◽  
Author(s):  
Stanley N. Roscoe ◽  
Scott G. Hasler ◽  
Dora J. Dougherty
Keyword(s):  
Image Magnification ◽  
Flight Experience ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Experience Effects ◽  
Detailed Determination ◽  
Accuracy Speed

The proficiency with which pilots can make takeoffs and landings using a periscope as the only source of outside visibility was studied under various conditions of flight. A detailed determination was made of the effects of variations in image magnification upon landing accuracy. Speed of transition to flight by periscope was related to flight experience. Effects of various weather, runway surface, and ambient lighting conditions upon flight by periscope were investigated.

A Practical Tool for Ambient Illumination Comparisons at Dusk/Dawn

2016 ◽  
Vol 60 (1) ◽  
pp. 470-474 ◽  
Author(s):  
Hilary Lam ◽  
Sayf Gani ◽  
Randy Mawson ◽  
Jason Young ◽  
Erin Potma
Keyword(s):  
Human Perception ◽  
Time Lapse ◽  
Time Of Day ◽  
Ambient Illumination ◽  
Adjustment Factor ◽  
Lighting Conditions ◽  
Accurate Knowledge ◽  
Ambient Lighting ◽  
Practical Tool ◽  
Sky Conditions

Nighttime visibility is an important consideration in collision reconstruction and personal injury investigation. Decreased contrast in low ambient lighting conditions can greatly affect human perception and response. Because ambient lighting levels change rapidly at dawn and dusk, forensic investigators must have an accurate knowledge of the time of day and the cloud conditions at the time of the incident before initiating a nighttime visibility assessment. Previously, human factors experts attempting re-enactments at dawn or dusk have had to wait for sky conditions that match those at the time of the incident, making the investigation of those cases extremely difficult, if not unfeasible. In this study, an ambient illumination equivalency tool has been developed based on a database of time-lapse light meter readings collected by the authors. This new tool can be used to facilitate nighttime visibility assessments on any day by providing a time adjustment factor to account for the changes in ambient illuminance due to differences in the cloud conditions between the day of the incident and the day of the re-enactment.

scholarly journals Software package for testing three-dimensional shape measurement methods using structured lighting

2021 ◽  
Vol 2057 (1) ◽  
pp. 012087
Author(s):  
S V Dvoynishnikov ◽  
V O Zuev ◽  
I K Kabardin ◽  
D V Kulikov ◽  
V V Rahmanov
Keyword(s):  
Software Package ◽  
Three Dimensional ◽  
Measurement Methods ◽  
Shape Measurement ◽  
Structured Lighting ◽  
Lighting Conditions ◽  
Ambient Lighting ◽  
Dimensional Shape ◽  
Shadow Maps ◽  
Three Dimensional Shape

Abstract This work aims at creating a universal software package for the development and testing of triangulation methods using structured lighting for measuring the three-dimensional geometry of objects in difficult ambient lighting conditions. As a result, a software package meeting the stated requirements is created. Lighting is based on the Fong model. A method for preloading objects is implemented to optimize the operation of the software package. An accelerated method for creating shadow maps is proposed and implemented. The developed software package is shown to successfully perform all required functions.

scholarly journals Case Study on the Impact of Artificial Light on Lighting Performance Quality for Architecture Studios

2021 ◽  
Vol 13 (3) ◽  
Author(s):  
N. A. Adnan ◽  
◽  
N. S. Sujali ◽  
N. D. Md Amin ◽  
◽  
...  
Keyword(s):  
Learning Experience ◽  
Comfort Level ◽  
Learning Space ◽  
Lighting Condition ◽  
Performance Quality ◽  
Engineering Society ◽  
Illuminance Level ◽  
The Impact ◽  
The City

A well-lit learning space is crucial to ensure the comfort of its occupants, especially for an architecture student who spends long hours in a studio to design, sketch, draw and build prototypes. This paper presents the results from a study conducted on the illuminance level of the architecture studios in the city campus of Universiti Tun Hussein Onn Malaysia (UTHM), Malaysia that were once laboratories. Measurements had been done using the Lux meter. Illuminance contours were generated using SigmaPlot and Dialux software for all the five rooms and compared with the requirements stipulated in the Malaysian Standard, Australia/New Zealand Standard and Illumination Engineering Society of North America (IESNA) standard for a room with similar function. A survey was also conducted among undergraduate architecture students who were using the studios daily to gauge their perception on the lighting condition and comfort level. The outcome of this study can be considered for future architecture studio lighting design to improve the students’ learning experience.

scholarly journals The impact of transition type on chromatic adaptation under dual lighting conditions

2020 ◽  
Vol 2020 (28) ◽  
pp. 36-41
Author(s):  
Shining Ma ◽  
Peter Hanselaer ◽  
Kees Teunissen ◽  
Kevin A.G. Smet
Keyword(s):  
Chromatic Adaptation ◽  
Spatial Complexity ◽  
Lighting Conditions ◽  
Adaptation State ◽  
Cat Model ◽  
The Impact ◽  
Transition Type

Over the years, many CATs (chromatic adaptation transform), typically based on the von Kries coefficient rule, have been developed to predict the corresponding colors under different illuminants. However, these CATs were derived for uniform stimuli surrounded by a uniform adapting field. To investigate the adaptation state under spatially complex illumination, an achromatic matching experiment was conducted under dual lighting conditions with three color pairs and two transition types. It has been found that the transition type has an impact on both the equivalent chromaticity and degree of adaptation. These results can help build a comprehensive von Kries based CAT model, with considering the spatial complexity of illumination.

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