Color quality scale

Abstract

The color rendering index ͑CRI͒ has been shown to have deficiencies when applied to white light-emitting-diode-based sources. Furthermore, evidence suggests that the restricted scope of the CRI unnecessarily penalizes some light sources with desirable color qualities. To solve the problems of the CRI and include other dimensions of color quality, the color quality scale ͑CQS͒ has been developed. Although the CQS uses many of elements of the CRI, there are a number of fundamental differences. Like the CRI, the CQS is a test-samples method that compares the appearance of a set of reflective samples when illuminated by the test lamp to their appearance under a reference illuminant. The CQS uses a larger set of reflective samples, all of high chroma, and combines the color differences of the samples with a root mean square. Additionally, the CQS does not penalize light sources for causing increases in the chroma of object colors but does penalize sources with smaller rendered color gamut areas. The scale of the CQS is converted to span 0-100, and the uniform object color space and chromatic adaptation transform used in the calculations are updated. Supplementary scales have also been developed for expert users.

A review of indices for assessing visual comfort with a view to their use in optimization processes to support building integrated design

“…Finally, since commercial lamps are improved with regards to some metrics, an unsuitable index could lead to yield wicked illuminants and hinder the development of new products and technologies. a 'saturation factor' that neglects those chromaticity shifts from the reference illuminant, which are more chromatic since they foster color quality if are not excessive [71]. Furthermore, the arithmetic mean is replaced by the root mean square deviation that amplifies large chromaticity shifts instead of averaging them with others…”

“…The former is called Color Fidelity Scale (Q f ) and aims at assessing the faithfulness of object color appearances by neglecting the saturation factor; the latter is called Color Preference Scale (Q p ) and aims "to indicate the overall quality of a light source" [71] by rewarding those light sources that increase the chromaticity of lit objects.…”

“…FCI estimates the color discrimination (here called 'feeling of contrast' or 'visual clarity') of a light source assuming that saturation is generally preferred in lighting applications [71,139].…”

“…The scaling factor "3.1" of Eq (34) has been chosen in order to have the General Color Quality Scale value (Q a ) equal to CRI for standard fluorescent lamps and to keep a good degree of consistency between Q a and CRI for traditional illuminants [71]. The formulation to calculate the single value output has been normalized to deliver a percentage value using the equation…”

Color Error in the Digital Camera Image Capture Process

“…The NIST color quality scale (CQS) color test chart was created from a set of saturated colors (NIST CQS #1-#17) that sample the range of perceived hues ( Fig. 2) [4]. The color patches are Munsell samples with a matte reflective surface, and are commercially available 1 .…”