Estimating Perceived Brightness in Low Luminance Conditions

2020 ◽  
pp. 33-49
Author(s):  
V.B. Pyasetsky
Keyword(s):  
Visual Perception ◽  
Analytical Solutions ◽  
Selection Criterion ◽  
Estimation Procedure ◽  
Engineering Practice ◽  
Colour Temperature ◽  
Mesopic Vision ◽  
Low Luminance ◽  
Artificial Illumination ◽  
Minimum Discrepancy

Mesopic photometry, which studies visual perception of low-level optical radiation, is of great interest today in lighting engineering. It involves investigating human responses to visual observations in low light conditions in the object space, determining the optimum artificial illumination levels in industrial areas, and solving clinical perimetry problems. The estimation procedure for mesopic photometry recommended by the International Commission on Illumination (CIE) is based on computing a combination of photopic (daylight) and scotopic (nighttime) visual perception levels. This procedure being iterative makes it inconvenient to apply in engineering practice, as the number of iterative steps proves to be several dozens on average, exceeding a hundred in certain cases. As a result, the feasibility of using the CIE procedure instead of a purely photopic perception technique becomes questionable. The discrepancy in the results obtained via these methods informs the selection criterion. The paper compares computation results for perceived brightness in photopic and mesopic vision in low luminance conditions. We also establish whether it is possible to find analytical solutions using the CIE procedure. We show that, for radiation of a colour temperature in the range of 950--12000 K, the maximum computational discrepancy between photopic and mesopic vision scenarios lies in the --200--50 % range, while the minimum discrepancy is approximately 5 % for radiation characterised by a colour temperature of approximately 2000 K. We also present analytical solutions for several specific cases according to the CIE procedure

Effect of correlated colour temperature and illuminance levels on user’s visual perception under LED lighting in Taiwan

Ergonomics ◽  
2019 ◽  
Vol 63 (2) ◽  
pp. 175-190 ◽  
Author(s):  
Wei-Cheng Chao ◽  
Li-Ying Hong ◽  
Min-Chih Hsieh ◽  
Eric Min-Yang Wang ◽  
Chi-Chin Yang ◽  
...  
Keyword(s):  
Visual Perception ◽  
Led Lighting ◽  
Colour Temperature

A Study on the Luminance of Landscape Lighting of Chinese Classical Architectures Based on Mesopic Vision

2011 ◽  
Vol 224 ◽  
pp. 175-178
Author(s):  
Li Ye Sun ◽  
Gang Liu ◽  
Hong Hai
Keyword(s):  
Subjective Evaluation ◽  
Qualitative Description ◽  
Experimental Result ◽  
Mesopic Vision ◽  
Cultural Connotation ◽  
Low Luminance ◽  
Quantification Analysis ◽  
Lighting Environment ◽  
The Relationship ◽  
Chinese Classic

Landscape lighting of Chinese classic architectures can reappearing the historical, cultural connotation and artistic appeal of architectures at night. Most of these scenes are low luminance and weak contrast, and the visual level is in mesopic vision. Taking the Summer Place as an example, considering the characteristics of vision in different luminance levels, this research obtains a series of simulant scenes with low luminance and weak contrast in mesopic vision by using physical quantity relations between the luminance of actual scene and reappearance scene. Utilizing experiment observation, computer simulation, quantification analysis and subjective evaluation, the research relate the quantitative index and the qualitative description and then realize the synthetically consideration of the relationship between the physics and the psychology stimulation in the lighting environment. Through the statistical analysis of experimental result, it suggests the satisfactory scope of the luminance and the luminance ratio. Similarly, the results of this research have significance to energy saving and the development of green lighting.

scholarly journals The calculation of variable heat flow in solids

1946 ◽  
Vol 240 (813) ◽  
pp. 1-57 ◽  
Keyword(s):  
Thermal Properties ◽  
Heat Flow ◽  
Analytical Solutions ◽  
Numerical Evaluation ◽  
Formal Solution ◽  
Industrial Processes ◽  
Laboratory Work ◽  
Engineering Practice ◽  
Direct Experiment ◽  
Variable Heat Flow

In many contexts, in laboratory work, in industrial processes and in engineering practice, situations arise in which it is required to determine the flow of heat in bodies under nonsteady conditions. In some cases this can be done by direct experiment, and a few cases are sufficiently simple for formal analytical solutions of the appropriate equations to be obtained and evaluated. But direct experiment is often difficult or impossible, especially under practical conditions of manufacture or operation; and often the conditions of the problem, such as inhomogeneity or the shape of the material, or variation of its thermal properties with temperature, either make the formal solution so complicated that its numerical evaluation is impracticable, or put a formal solution out of the question altogether.

Computational Mechanics

1985 ◽  
Vol 38 (10) ◽  
pp. 1282-1283 ◽  
Author(s):  
A. Needleman
Keyword(s):  
Mechanical Behavior ◽  
Computational Methods ◽  
Analytical Solutions ◽  
Solid Mechanics ◽  
Computational Mechanics ◽  
Mechanical Systems ◽  
Engineering Practice ◽  
Computational Capability ◽  
Engineering Problems ◽  
Complex Engineering

Computational methods play a key role in solid mechanics, as a way of modelling fundamental aspects of mechanical behavior, as a vehicle for transferring this improved modelling capability into new engineering tools, and as a means of utilizing these tools in engineering practice. Modern computational methods enable realistic models of mechanical systems to be formulated without regard as to whether or not analytical solutions are feasible. Increased computational capability is also an incentive for developing more accurate theories, since it becomes possible to use such theories to solve complex engineering problems.

scholarly journals METAMERISM INDEX OF LED LIGHT ON HALFTONE COLOUR IMAGES

2021 ◽  
Vol 30 (2) ◽  
pp. 1-9
Author(s):  
Igor Zjakić ◽  
◽  
Ivana Ljevak ◽  
Albulena Bilalli ◽  
◽  
...  
Keyword(s):  
Visual Perception ◽  
Skin Color ◽  
Large Change ◽  
Limited Range ◽  
Light Sources ◽  
Light Conditions ◽  
Colour Temperature ◽  
Led Light ◽  
Lighting Conditions ◽  
Small Index

Skin face detection in photo imaging, is an important component of systems for detecting similarities in visual perception, tracing faces through illumination and metamerism. This paper presents an evaluation of the skin perception under standardized conditions of varied light sources: cool-white fluorescent “store light”, 6500K fluorescent “daylight”, and incandescent “home light”, Led light 6500 K, 2700K, 4000K CCT. In cases where the discrepancy is large, the resulting index of metamerism can be misleading. A small index of metamerism and a large change of color under illuminant metamerism has a different interpretation than what is perceived. This has been demonstrated through small colour variations in print through CMYK colors. The implication is that particular indices of metameric should only account for a limited range under different light conditions. The method used in this paper is based on visual perception, which aim to work with a wide variety of individuals, under varying lighting conditions under the influence of standard daylight, but in this case we also used the Led light 6500K correlated colour temperature, and variations of skin color tones, comparing the illuminant metamerism of visual perception based on different reflectance power distributions (SPDs).

Properties of Light Sources under Mesopic Vision

2011 ◽  
Vol 308-310 ◽  
pp. 228-231
Author(s):  
Yong Yang ◽  
Lei Wang ◽  
Wei Li
Keyword(s):  
Visual Perception ◽  
Luminous Efficiency ◽  
Light Sources ◽  
Human Visual Perception ◽  
Efficiency Function ◽  
White Leds ◽  
Mesopic Vision ◽  
Vision Condition ◽  
Background Brightness

The mesopic vision theory is used to study illumination properties of series of light sources, through the test of luminous spectrum and derivation based on the MOVE model, the results show that spectral luminous efficiency function Vmes(λ) is between traditional V(λ) and V′(λ) when the background brightness under mesopic vision condition, and the function of Vmes(λ) is changed with the different of light sources and background brightness. Based on human visual perception, the mesopic vision equivalent brightness can be calculated, which of HPS is lower than test brightness corrected by V(λ), but white LEDs and FL show opposite phenomena, and the different value between mesopic and photopic brightness presents reduce trend with rising of background brightness.

Population Balances Involving Aggregation and Breakage Through Homotopy Approaches

2018 ◽  
Vol 16 (6) ◽  
Author(s):  
Abhishek Dutta ◽  
Zehra Pınar ◽  
Denis Constales ◽  
Turgut Öziş
Keyword(s):  
Analytical Solutions ◽  
Nonlinear Problems ◽  
Difficult Problem ◽  
Simple Problem ◽  
Engineering Practice ◽  
Mathematical Framework ◽  
Transform Method ◽  
Approximate Analytical Solutions ◽  
Homotopy Analysis ◽  
Population Balances

Abstract Homotopy techniques in nonlinear problems are getting increasingly popular in engineering practice. The main reason is because the homotopy method deforms continuously a difficult problem under study into a simple problem, which then can be easy to solve. This study explores several homotopy approaches to obtain semi- or approximate analytical solutions for various cases involving mechanistic phenomena such as aggregation and breakage. The well-established approximate analytical methods namely, the Homotopy Perturbation Method (HPM), the Homotopy Analysis Method (HAM), and the more recent forms of homotopy approaches such as the Optimal Homotopy Asymptotic Method (OHAM) and the Homotopy Analysis Transform Method (HATM) have been used to solve using a general mathematical framework based on population balances. In this study, several test cases have been discussed such as conditions in which the aggregation kernel is not only constant, but also sum or product dependent. Furthermore cases involving pure breakage, pure aggregation and a combined aggregation-breakage have been studied to understand the sensitivity of these homotopy-based methods in solving PBM. In all these cases, the solutions have been analytically studied and compared with literature. Using symbolic computation and carefully chosen perturbation parameters, the approximate analytical solutions are compared with each other and with the available analytical solution. A convergence analysis of the solution methods is made in comparison to the available solution. The case studies indicate that OHAM performs slightly better than both HATM and HPM in solving nonlinear equations such as the PBEs.

Gradient-Related Non-Photorealistic Rendering for High Dynamic Range Images

2013 ◽  
Vol 17 (4) ◽  
pp. 628-636 ◽  
Author(s):  
Jiajun Lu ◽  
◽  
Fangyan Dong ◽  
Kaoru Hirota
Keyword(s):  
Visual Perception ◽  
Dynamic Range ◽  
Digital Images ◽  
High Dynamic Range ◽  
Experimental Results ◽  
Range Images ◽  
Source Information ◽  
Photorealistic Rendering ◽  
Low Luminance ◽  
High Dynamic

A non-photorealistic rendering (NPR) method based on elements, usually strokes, is proposed for rendering high dynamic range (HDR) images to mimic the visual perception of human artists and designers. It enables strokes generated in the rendering process to be placed accurately on account of improvements in computing gradient values especially in regions having particularly high or low luminance. Experimental results using a designed pattern show that angles of gradient values obtained from HDR images have a reduction in averaged error of up to 57.5% in comparison to that of conventional digital images. A partial experiment on incorporating HDR images into other NPR styles, such as dithering, shows the wide compatibility of HDR images in providing source information for NPR processes.

Employees’ Perspective for Employment Opportunities Created Under CPEC: Case Study of Coal Fire and Solar Project in Punjab, Pakistan

2021 ◽  
Author(s):  
Ramsha Saleem ◽  
Shahzada M. Naeem Nawaz ◽  
Altaf Hussain
Keyword(s):  
Sample Selection ◽  
Selection Criterion ◽  
Principal Component ◽  
Estimation Procedure ◽  
Primary Data ◽  
Employment Opportunities ◽  
Strategic Investment ◽  
Narrative Methods ◽  
Coal Fire ◽  
The Impact

Abstract China Pakistan Economic Corridor is an important milestone which provides opportunity to host strategic investment in Pakistan, primarily in infrastructure and power projects. At the same time, it has shown its potential to directly and indirectly influence the employment. In this perspective, it is significant to understand the perception of employees working in CPEC projects. Accordingly, the aim of the current study is to analyze perception of employees of Sahiwal Power Project and Quaid-e-Azam Solar Power projects. The study employed the descriptive analytical narrative methods at first stage. Then, it adopted OLS estimation procedure to estimate the impact of various relevant indicators on perception of workers about employment opportunities. Primary data is based upon structured questionnaire of employees of the projects on sites whereas the sample selection criterion is statistically rigorous. Using Principal Component Analysis (PCA) and response to relevant questions, four indices are constructed for opportunity in CPEC (CO), social change (SC), coal projects (CP) and employment opportunities (EO). The other determinants of EO are education level and area of belonging. The results suggest that policy makers should focus more on developing the skill level of labor force so that more benefits can be accrued from the investments in various projects. It can be made easy through developing close linkage between the universities and industry.

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