Kreft's dichromaticity index (DI) is a
measure for quantification of
dichromatism
Dichromatism (or polychromatism) is a phenomenon where a material or solution's hue is dependent on both the concentration of the absorbing substance and the depth or thickness of the medium traversed. In most substances which are not dichromatic, ...
. It is defined as the difference in
hue
In color theory, hue is one of the main properties (called color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that ...
angle (Δh
ab) between the
color
Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...
of the sample at the dilution, where the
chroma (color saturation) is maximal, and the color of four times more diluted (or thinner) and four times more concentrated (or thicker) sample. The two hue angle differences are called the dichromaticity index towards lighter (Kreft's DI
L) and
dichromaticity index towards darker (Kreft's DI
D) respectively.
Kreft's dichromaticity indexes DI
L and DI
D for
pumpkin seed oil
Pumpkin seed oil is a culinary oil, used especially in central Europe.
Culinary uses
This oil is a culinary specialty from what used to be part of the Austro-Hungarian Empire and is now southeastern Austria (Styria), eastern Slovenia (Styria ...
, which is one of the most dichromatic substances, are −9 and −44, respectively. This means, that pumpkin seed oil changes its color from green-yellow to orange-red (for 44
degrees in
Lab color space
The CIELAB color space, also referred to as ''L*a*b*'' , is a color space defined by the International Commission on Illumination (abbreviated CIE) in 1976. (Referring to CIELAB as "Lab" without asterisks should be avoided to prevent confusio ...
) when the thickness of the observed layer is increased from cca 0.5 mm to 2 mm; and it changes slightly towards green (for 9 degrees) if its thickness is reduced for four-fold.
The color of pumpkin oil at increasing thickness or concentration presented in
CIELAB
The CIELAB color space, also referred to as ''L*a*b*'' , is a color space defined by the International Commission on Illumination (abbreviated CIE) in 1976. (Referring to CIELAB as "Lab" without asterisks should be avoided to prevent confusio ...
colorspace diagram. Straight lines are vectors showing hue (angle) and chroma (length) of the color at maximal chroma (toward the square mark), and the colors of four-fold less or more diluted or thick pumpkin oil (DI
L and DI
D). Note that DI
D is −44.1 degrees and DI
L corresponds to −8.97 degrees.
Dichromaticity (DI
L and DI
D) of selected substances, calculated from their VIS absorption spectra by the computer algorithm “Dichromaticity index calculator”:
Maximal chroma: chroma at concentration (thickness) where the color of the substance has maximal chroma (saturation). Angle at maximal chroma: the hue, which is represented by the angle of the vector to the color with maximal chroma in the CIELAB colorspace diagram.
References
External links
Free Dichromaticity Index Calculator software
{{DEFAULTSORT:Kreft's Dichromaticity Index
Optics
Color
Index numbers
Scales
Spectroscopy