The color rendition engine based on the statistical metric allows us to uniquely quantify the characteristics of color quality of illumination and assess the color rendition preferences. We now report on using the color rendition engine for revealing individual and cultural differences in color quality preferences of 205 American and Chinese subjects. Our study demonstrated that the majority of individuals preferred the color blend with the same statistical figures of merit on the average but with a much larger spread of blends for Americans. For both groups, the color rendition preferences depended on the object being illuminated. This was demonstrated by illuminating a set of common colored objects and three different paintings. We conclude that the color quality of lighting can be optimized and enhanced using the feedback to change the spectral power distribution of the illuminating source depending on the object being illuminated and on the preferences of an individual observer and a cultural group.
We consider the energy-saving potential of solid-state street lighting due to improved visual performance, weather
sensitive luminance control and tracking of pedestrians and vehicles. A psychophysical experiment on the measurement
of reaction time with a decision making task was performed under mesopic levels of illumination provided by a highpressure
sodium (HPS) lamp and different solid-state light sources, such as daylight and warm-white phosphor converted
light-emitting diodes (LEDs) and red-green-blue LED clusters. The results of the experiment imply that photopic
luminances of road surface provided by solid-state light sources with an optimized spectral power distribution might be
up to twice as low as those provided by the HPS lamp. Dynamical correction of road luminance against road surface
conditions typical of Lithuanian climate was estimated to save about 20% of energy in comparison with constant-level
illumination. The estimated energy savings due to the tracking of pedestrians and vehicles amount at least 25% with the
cumulative effect of intelligent control of at least 40%. A solid-state street lighting system with intelligent control was
demonstrated using a 300 m long test ground consisting of 10 solid-state street luminaires, a meteorological station and
microwave motion sensor network operated via power line communication.
Versatile spectral power distribution of solid-state light sources offers vast possibilities in color rendition engineering.
The optimization of such sources requires the development and psychophysical validation of an advanced metric for
assessing their color quality. Here we report on the application and validation of the recently introduced statistical
approach to color quality of illumination. This new metric uses the computational grouping of a large number of test
color samples depending on the magnitude and direction of color-shift vectors in respect of just perceived differences of
chromaticity and luminance. This approach introduces single-format statistical color rendition indices, such as Color
Fidelity Index, Color Saturation Index and Color Dulling Index, which are the percentages of test color samples with
particular behavior of the color-shift vectors. The new metric has been used for the classification of practical phosphor
conversion white light-emitting diodes (LEDs) and polychromatic LED clusters into several distinct categories, such as
high-fidelity, color saturating, and color dulling light sources. We also report on the development of the tetrachromatic
light source with dynamically tailored color rendition properties and using this source for the psychophysical validation
of the statistical metric and finding subjective preferences to the color quality of lighting.
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