OptLab-SPX   CIE Color Measurement Calculations

Color calculations are employed to describe the color of transparent and reflective samples in an objective way. As a starting point the transmission or reflection spectrum of the sample in the visible range is used. With this spectrum the process of human color vision is mathematically copied with standardized data sets; as a result a set of 3 values is generated, which describe the color of a sample objectively and definitely. The calculation process applies specific illumination and angle of vision. Since these parameters influence the resulting data triplet, they must be given for each set of color values.

Originally these procedures were defined by CIE, but have now found their way into many national and international standards like DIN 5033 or ASTM E-308.

OptLab-SPX performs the color calculations according to the standards. The spectra must have been scanned on an absolute basis in the wavelength range of either 400 - 700 nm or 380 - 780 nm. Alternatively also calculations according to the new DIN EN ISO 11664 may be executed, see below.
Both %R and %T spectra can be used. The following result triplets are available in OptLab-SPX:

            Tristimulus values X, Y, Z
            Color coordinates x, y and tristimulus value Y
            Color coordinates x, y, z
            CIE color coordinates L*, a*, b*
            CIE color coordinates L*, C*, h* (optionally also S = C / L)

The following standardized illuminants are available:

            A             light of a light bulb
            C            daylight with clouded sky
            D65        daylight with clear sky and high sun

CIE Lab* values can also be calculated with illuminants F2, F7, F11 as well as D50, D55, D75

The available observer angles of view are 2 degrees (focussed viewing, CIE 1931) and 10 degrees (broad-range viewing, CIE 1964).

Optlab-SPX also offers calculation of X, Y, Z and CIE L*a*b* color values following the latest norms DIN EN ISO 11664-1..6 of the years 2007-2014. In contratst to older norms, the spectral data of the range 360-830 nm are applied; see also CIE color difference.

The OptLab-SPX calculations are based on data sets, which comprises the necessary illuminants and observer data . The user may generate additional data files following the OptLab-SPX conventions to extend the scope of illuminants, wavelength ranges and observers. As well, the user may modify the result designations. Color values typically are generated as a set of 3 values, but any single value can also be output. For each result value the number of decimal places can be defined.