Qiyan Zhai

The impact of illuminance and colour temperature on viewing fine art paintings under LED lighting

The aims of this study were to investigate suitable LED lighting conditions for viewing fine art paintings in a museum environment and to test Kruithofs rule that defines pleasant lighting in terms of correlated colour temperature (CCT) and illuminance. The experiment was conducted in a room designed to simulate the exhibition of real paintings in museums. Twenty-four observers of different gender and educational background participated to evaluate oil and gouache paintings under different lighting conditions. Each painting was assessed via 14 word pairs using the categorical judgment method. The results showed that illuminance had a larger impact than CCT on visual perception, and three factors dominate visual perceptions: Comfort, Vividness and Definition. The present results only partially agreed with Kruithofs rule. A comfort zone of illuminance and CCT for paintings in museums has been developed.

The impact of LED on human visual experience

High flexibility of LED offers possibility to adjust parameters of lighting, like CCT (correlated color temperature), luminance, and spectral power distribution so that lighting can be made to have positive effects on people. This experiment investigated the effects of available lightings on visual performance and atmosphere feeling. Lightings in the experiment included: LED, energy-saving lamp, tungsten, and a smart lighting product from Philips. 10 participants were asked to complete the experiment tasks and a questionnaire. The experimental tasks include: critical flickering frequency (CFF), calculation, proofreading, reading comprehension and a concentration test (d2 test). They were designed to test the visual performance of participants. The questionnaire was made up of categorical judgment of the atmosphere of lighting environment. It was designed to study the influences of lighting on peoples perception of atmosphere in the environment. The result revealed that Hue-energetic (6300K, 150cd/m2) made people performed best and that CCT and perception of brightness affected peoples feeling of activeness and comfort. Furthermore, it also confirmed that blue light could trigger energetic arousal.

The impact of LED lighting parameters on viewing fine art paintings

This study investigated the main visual perceptions and the optimal LED lighting parameters for viewing museum paintings. Oil and gouache paintings seen under different LED illuminants were assessed using the categorical judgement method. It was found that ‘visibility’ and ‘warmth’ are the main perceptions for viewing paintings. The results showed that a correlated colour temperature around 3500 K, a negative deviation of the target from the blackbody locus and a high colour rendering index can achieve satisfactory results. The difference between colour fidelity-based colour rendering indices and colour preference-based colour rendering indices for a museum application was also explored.

Atmosphere perception of dynamic LED lighting over different hue ranges

This paper investigates the atmosphere perception of dynamic coloured lighting over warm and cool hue ranges in a living room. Experiments were carried out with eight fully functional multi-channel tunable LED luminaires. Thirty Chinese observers (14 males and 16 females) evaluated 36 light conditions (2 luminance ×2 chroma ×3 hue range types ×3 speeds) using a questionnaire of 25 response scales. Four atmosphere factors were extracted: coziness, spaciousness, liveliness and warmth. Both dynamics and hue range significantly affected the atmosphere perception.

Atmosphere perception of LED dynamic lighting with color varied in cool and warm hue

Take the perspective of cool hue and warm hue, this paper investigated atmosphere perception of LED dynamic colored lighting, as well as physical parameters effects. An experiment was carried out in a LED lighting lab with 8 fully functioned LED cubes, which can produce temporal color-varied lighting. 30 Chinese observers (14 males, 16 females, mean age=25.43, SD= 2.86) evaluated 36 Light conditions (2 lightness levels × 2 chroma levels × 3 hue range types × 3 speed) with 25 word pairs questionnaire. 4 atmosphere dimensions were extracted as coziness, soberness, liveliness and warmness. High speed and high chroma is helpful to create liveliness; low speed and low chroma is more cozy. Warm hue range makes intimate and warm space; cool hue range usually increase soberness. Differences caused by gender and design background were also found.

Investigation of Memory Colors of Chinese Observers

Long-term memory colors of familiar objects are of great significance in the applications such as imaging, lighting, and color reproduction. Previous studies of memory color were mainly conducted on the surface color samples under variable illuminations or images presented on displays. In this work, memory colors of Chinese observers with a set of 22 familiar objects have been investigated on a well-calibrated display. A specially developed psychophysical method and an operational program were applied for the observers to match the homogenous patch colors through object name descriptions with their memory colors on a self-luminous monitor in a given viewing situation. The results of inter-observer variability were analyzed in CIELAB color space by mean of color differences from the mean (MCDM) and tolerance ellipse. The two indexes were found to be consistent. Our aim is to establish a methodology both to study memory colors and to quantify the specific Chinese memory colors, which can benefit for further image enhancement.

A Brief Review of Colour Quality Assessments of LED Lightings for Museums

Recent years the subject of colour quality of LED lighting in museum was extensively studied. It was found that different experimental results can be effectively described as Comfort Zone in terms of illuminance and colour temperature of the museum illuminations. Work of updating colour rendering index for LED lighting can also be used for museum lighting applications. Recent studies on museum lighting and some related work are reviewed in this paper. Important recommendations about how to achieve high colour quality museum lighting are also given.