Ingineria Iluminatului - Journal of Lighting Engineering - Prof. Florin ...

quantities, because the tangential directions of hue circles and equi-chroma loci in these spaces do not meet at right angles
mutually, i.e., the direction of hue shift and that of chroma shift are not orthogonal to each other. Furthermore, the
independence and orthogonality between metric-correlates of hue and chroma had not been accomplished yet.
By contrast, hue circles which are warped in the conventional colour spaces approach uniform circles in new colour
space NC-IIIC. The coordinates of colours with same chroma lie on a circle of constant radius in new colour space
NC-IIIC. So chroma can be expressed as the radius of hue circle, i.e., metric-chroma, and hue will be indicated by the hue
angle, i.e., metric-hue, independently. This space can show hue, lightness and chroma in orthogonal directions. In this new
space, the relative deviation of Hue circle from the circumference is reduced from 13.614.5 % to 1.26 % , i.e., the
uniformity in the direction of chroma is improved to the level of almost completeness for practical purposes.
Figure 2 Hue circles of Munsell colours with value of 6 in uniform colour spaces
4. Subjective Evaluation Of Perceived Colour Appearance
4.1 Test colours for visual experiment
Test colour samples are 40 colours which are selected from Munsell colour samples with value of 6 and chroma of 8. A
list of test colour samples with Munsell notation is shown in Table 1.
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INGINERIA ILUMINATULUI 15-2005