Perceptual responses to LED illumination with colour rendering indices of 85 and 97

Mao, Wei; Houser, Kevin W.; David, Aurélien; Krames, Michael R.

doi:10.1177/1477153514548089

Cited by 47 publications

(55 citation statements)

References 26 publications

(37 reference statements)

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“…It can be observed that the color differences with the GW algorithm were similar for all the patches; while those with the RM varied a lot. Though the FWA excitation created blue tints and produced blue shifts, the largest color differences with the RM algorithm not only happened to bluish patches (e.g., Patches 7,12,17,19,20,and 22) but also to the neutral patches (e.g., Patches 5 and 6). The comparisons of the balanced B values (i.e., B 0 ) of each patch between these two pairs of images, as shown in Figure 14, suggest that the color differences caused by the 14 the results clearly revealed that the failure of blue-pumped white LEDs in rendering FWAenhanced whites can cause noticeable color difference not only to human perception of white appearance of surface colors, but also to the appearance of various colors produced by imaging systems using white balance algorithms.…”

Section: Discussionmentioning

confidence: 99%

“…14 Typical blue-pumped white LEDs that are gradually becoming dominant in general illumination, however, contain little violet or ultraviolet radiation, 14,15 which has been found to affect significantly the whiteness appearance of surface colors perceived by humans. [16][17][18] Though FWA excitation plays an important role in the color appearance of white surfaces, its impact on white balance algorithms has never been investigated. In this study, a setup containing a Macbeth ColorChecker and one of three diffuse acrylic whiteness standards with different amount of FWAs was captured under four illuminants having different levels of CCT and UV/violet radiation, with a goal to investigate the impact of FWA excitation on white balance algorithms.…”

Section: Color Appearance Of White Surfaces and White Balance Algormentioning

confidence: 99%

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Impact of fluorescent whitening agent excitation on White Balance Algorithms

Chen

Mao

2018

Color Research & Application

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Various white balance algorithms, based either on the Gray World assumption or on the Retinex theory, have been developed to remove the color cast of illumination in images. Though most man-made white objects contain different amount of fluorescent whitening agents (FWAs) to enhance and create different degrees of whiteness appearance, the FWA excitation has seldom been considered in white balance algorithms. In this study, four illuminants, comprising 2 levels of CCT and 2 levels of UV/violet radiations, were produced to illuminate a setup, which included a Macbeth ColorChecker and a calibrated whiteness standard. Three whiteness standards containing different amount of FWAs were used under each illuminant, with one present each time. It was found the FWA excitation generally caused little color difference to the algorithms based on the Gray World assumption, which was likely due to the small size of the whiteness standard in the image. In contrast, the performance of the algorithms based on the Retinex theory was largely affected by the FWA excitation, as the FWA excitation affected the RGB values of the pixels for adjusting the gain factors. Given the wide usage of blue-pumped white LEDs that contained little UV/ violet radiation for enhancing luminous efficacy in general illumination, the impact of the FWAs is not trivial and should be considered in developing white balance algorithms. K E Y W O R D S color difference, fluorescent whitening agents (FWAs), LED, image quality, White balance algorithms Color Res Appl. 2018;1-12. wileyonlinelibrary.com/journal/col V C 2018 Wiley Periodicals, Inc. | 1

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Section: Discussionmentioning

confidence: 99%

Section: Color Appearance Of White Surfaces and White Balance Algormentioning

confidence: 99%

Impact of fluorescent whitening agent excitation on White Balance Algorithms

Chen

Mao

2018

Color Research & Application

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“…3. The change of the gamut shape was purposely designed, because both red and green were dominant colors in the painting and past studies have clearly suggested the important role of red in color preference evaluations Wei, Houser, Allen, and Beers 2014;Wei, Houser, David, and Krames 2014). All of the light settings were designed to be metameric, with a correlated color temperature (CCT) of 3000 K and a D uv of −0.005.…”

Section: Light Settings and Observers' Evaluationsmentioning

confidence: 99%

“…Most psychophysical experiments investigating color preference, including those described above, were conducted under a single illuminance level between 200 and 500 lx (Islam et al 2013;Jost-Boissard et al 2009Lin et al 2014Lin et al , 2015Liu et al 2013;Ohno et al 2015;Rea and Freyssinier 2010;Szabo et al 2014;Teunissen et al 2016;Veitch et al 2014;Houser 2016, 2017;Wei, Houser, Allen, and Beers 2014;Wei, Houser, David, and Krames 2014;. Such a range not only ensured that the illuminance was within the range of photopic vision but also covered most of the recommended illuminance levels for general illumination (DiLaura et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Consideration of Light Level in Specifying Light Source Color Rendition

Mao

Bao

Huang

2018

LEUKOS

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In lighting practice, light level is seldom considered when specifying light source color rendition. Many past studies found that sources that can enhance color saturation within a certain range, especially for red colors, were preferred, but the experiments were typically carried out with an illuminance between 200 and 500 lx and the illuminance was seldom varied in individual studies. This article reports a psychophysical study that was designed to test whether illuminance affected color preference. Four nearly metameric stimuli with a correlated color temperature (CCT) around 3000 K and a D uv of −0.005 were produced to illuminate an oil painting at two illuminance levels (that is, 20 and 500 lx). These four stimuli were carefully designed to cover a range of relative gamut (that is, IES R g) from 100 to 125 and enhance the saturation of red and green colors (that is, R cs,h1 and R cs,h8). Observers compared pairs of light stimuli at a same illuminance level in a sequential mode and selected the one under which he or she preferred the color appearance of the painting. It was found that the R g of the most preferred stimulus decreased as the illuminance increased. The stimulus with an R g ≈ 117 was the most preferred at 20 lx, whereas the one with an R g ≈ 100 was the most preferred at 500 lx. The interaction between illuminance and saturation enhancement caused by the stimuli with larger gamut areas revealed the importance of considering illuminance when specifying light source color rendition, especially when an application requires a low light level and good color rendition.

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“…Such problems are particularly solved by replacement of blue LED chip by violet one, following two phosphors technology [15,16]. Unfortunately the authors have any such light source for disposal during presented experiment.…”

Section: Methodsmentioning

confidence: 99%