D50 is scientific shorthand for a standard illuminant : the daylight spectrum at a correlated color temperature of 5000 K . Similar definitions exist for D55, D65 and D75.
12.
The color temperature ( as well as the correlated color temperature defined above ) may differ largely from the effective temperature given by the radiative flux of the stellar surface.
13.
The CRI of a light source does not indicate the apparent color of the light source; that information is under the rubric of the correlated color temperature ( CCT ).
14.
The second vector ( S 1 ) corresponds to yellow blue variation, accounting for changes in the correlated color temperature due to presence or absence of clouds or direct sunlight.
15.
To construct a daylight simulator of a particular correlated color temperature one merely needs to know the coefficients M 1 and M 2 of the characteristic vectors S 1 and S 2.
16.
Daylight has a spectrum similar to that of a black body with a correlated color temperature of 6500 K ( D65 viewing standard ) or 5500 K ( daylight-balanced photographic film standard ).
17.
A standard was developed, ANSI C78.377-2008, that specified the recommended color ranges for solid-state lighting products using cool to warm white LEDs with various correlated color temperatures.
18.
A notional temperature, the correlated color temperature, the temperature of a black body which emits light of a hue which to human color perception most closely matches the light from the lamp, is assigned.
19.
While these newer sources can still achieve correlated color temperatures and illuminance levels that are within the comfortable region of the Kruithof curve, variability in their color rendering indices may cause these sources to ultimately be displeasing.
20.
From these findings, it is evident that color rendering index, in place of correlated color temperature, may be a more appropriate metric for determining as to whether or not a certain source is considered pleasing.
