Assessment of Color Discrimination of Different Light Sources

Light quality is a key parameter of building design, which is mainly defined by the perceived luminance and the color rendering. Nowadays, there is a wide variety of metrics that do not converge in the color rendition evaluation of current light sources. The obsolescence of the Color Rendering Index promoted the rise of new procedures to provide an accurate evaluation. However, the score provided by most of these metrics does not distinguish between color deviation and hue discrimination, giving a single value to assess the overall color perception allowed by a light source. In this context, a new study is proposed, based on the evaluation of seven different light sources, comparing the results of the most recent color rendering metrics and those observed using a Farnsworth–Munsell trial carried out with 115 participants. The results obtained show that there is a notable divergence between color rendition and hue discrimination, although there is a clear proportionality between both. Moreover, a clear relationship is observed between color discrimination and the correlative color temperature of light sources, providing a better hue distinction with cool light sources, even though the psychological preferences of the participants do not coincide with the optimal scenario for color discrimination.

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The effects of illuminance, color temperature and color rendering index of light sources upon comfortable visual environments

Journal of Light & Visual Environment ◽

10.2150/jlve.1.2_31 ◽

1977 ◽

Vol 1 (2) ◽

pp. 31-39 ◽

Cited By ~ 22

Author(s):

Tenji WAKE ◽

Tadashi KIKUCHI ◽

Keishiro TAKEICHI ◽

Masaru KASAMA ◽

Hisashi KAMISASA

Keyword(s):

Color Temperature ◽

Light Sources ◽

Color Rendering Index ◽

Color Rendering

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Modeling of Selected Lighting Parameters of LED Panel

Energies ◽

10.3390/en13143583 ◽

2020 ◽

Vol 13 (14) ◽

pp. 3583 ◽

Cited By ~ 2

Author(s):

Krzysztof Baran ◽

Antoni Różowicz ◽

Henryk Wachta ◽

Sebastian Różowicz

Keyword(s):

Cooling System ◽

Luminous Flux ◽

Junction Temperature ◽

Color Temperature ◽

Light Sources ◽

Factors Influencing ◽

Forward Current ◽

Color Rendering Index ◽

Simulation Results ◽

Color Rendering

Semiconductor light sources are currently the fastest growing and most energy efficient group of light sources used in lighting technology. Their lighting parameters, such as luminous flux, correlated color temperature and color rendering index depend on the value of the forward current, as well as the temperature of the junction. LED source manufacturers usually specify, in data sheets, the effect of junction temperature and forward current on the luminous flux for individual light sources. The difficulty, however, is the correct determination of temperature and then lighting parameters, by simulation methods for multi-source lighting systems. Determining the junction temperature which affects lighting parameters is particulary important in the case of LED panels and luminaires, where thermally coupled LED sources shaping the output lighting parameters are in close proximity to each other. Additionally, other factors influencing the temperature distribution of sources, such as the design and geometry of the cooling system, the design of the printed circuit and thermal interface material used, should be considered. The article is a continuation of the publication in this journal where the influence of factors influencing the temperature distribution of the LED panel is presented. The purpose of the research in this article was to confirm the possibility of using CFD (Computational Fluid Dynamics) software, as well as to determine the accuracy of the results obtained in the temperature analysis of the multi-source LED panel, and in determining the output lighting parameters of the LED panel based on it. In this article, based on previously published research, a LED panel model with a cooling system was made, and then the CFD software determined the junction temperature of all light sources. The determined temperature of the LED sources constituted the basis for determining the output lighting parameters of the panel: luminous flux, color temperature and color rendering index. The simulation results were verified by real measurements on the constructed LED panel prototype. The LED panel temperature difference between the simulation results and the real results on the prototype did not exceed 5%. Moreover, the error of lighting parameters between the simulation results obtained and the results on the LED panel prototype in the worst case was 4.36%, which proves the validity and accuracy of simulation studies.

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New Color Rendering Metrics

Metrology and instruments ◽

10.33955/2307-2180(1)2020.37-44 ◽

2020 ◽

pp. 37-44

Author(s):

L. A. Nazarenko ◽

O. M. Didenko ◽

D. O. Usichenko

Keyword(s):

Light Source ◽

Human Perception ◽

Color Temperature ◽

Critical Parameters ◽

Human Observer ◽

Light Sources ◽

Color Information ◽

Area Index ◽

Color Rendering Index ◽

Color Rendering

Color is not a physical properly of object, but rather a human perception enabled by light. Nevertheless the color of light sources is described by the industry primarily in terms of two metrics, correlated color temperature (CCT) and color rendering index (CRI), that are only indirectly related to human perception. CCT is intended to characterize the appearance of the illumination generated by source, and CRI is intended to characterize the appearance of objects illuminated be the source. There two color metrics developed nearly of half-century ago, are increasingly being challenged because new source are being developed with increasingly exotic spectral power distribution. The new color metric applicable to the color appearance of the light emitted by at light source and quantified by the CCT and D. The chromaticity is one of the critical parameters for light sources for general lighting and normally specified with chromaticity coordinates CIE (x, y) or (', '). However these two numbers do not provide the color information intuitively. For practical purposes, collated color temperature (CCT) is commonly used to provide the chromaticity information of general illumination source CCT, however, provides only one dimension of the chromaticity and there is another dimension, which is the position of chromaticity with respect to Plancian locus. For this purpose «D» or similar terms as distance from Plancian locus have been need used in some part at the industry but these had not beer officially defined is any standard. Color rendering is general term for describing the ability of a light source to provide color information to human observer when objects are illuminated by that source like CCT color rendering index (CRI), the most accepted measure of color rendering. CRI was developed, through the system of colorimetry, simply to be an indication of how «natural» or «undistorted» the light source makes the color of objects appear when illuminated by the source when used as the sole measure of color rendering for a light source, CRI simply cannot meet expectations. With the advent of SSL, these limitations have become more widely recognized. It was proposed a two-metric system combining CRI, a measure of color consistency with respect to a reference source, with gamut area index (GAI), a measure of color saturation. When used to gather, the two metrics appear to optimize the color appearance of natural objects like fruits and vegetable enhancing their vividness with making them appear unnatural. CCT is shown in commercial instruments but D is often available. D needs to be calculated using the method of triangular solution: Create a table CCT is distance di to Plancian locus on () coordinate; Find the closest point in the table; Solve the triangle for the neighboring 2 points. Gamut area of light source is commonly calculated as the area of the polygon defined by the chromaticities in CIE 1977 (', ') color space of the light CIE TCSs. Gamut area of EES is sealed to 100 and defined as gamut area index. The gamut area of any other light source is scaled accondingle.

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