Measure the Illuminance, Correlated Color Temperature and Color
Rendering Index (CRI) & Television Lighting Consistency Index
(TLCI) of an illuminant.
A spectrometer type instrument is needed to compute the CRI.
- With the instrument configured with it's ambient measurement
diffuser in position, measure the illuminant at the desired
- The XYZ Readout Y (middle) value will be the illumination
level in Lux
- CCT is the standard CIE 1960 UCS closest temperature to the
black body illuminant locus. Alternate measure of temperature
such as using a modern delta E measure, or the Daylight locus
can be selected by modifying the Color
- The CIE 1995 Color Rendering Index value is a measure of
spectral quality, 100 being the maximum possible. By default the
R9 value will also be shown, which can be useful in judging how
lighting renders saturated Reds, as poor Red rendering isn't
always evident in the Ra value. An R9 value above 0 is generally
considered a minimum requirement for rendering of reds. The
values will be annotate with (Invalid) if the color is
not within the standard tolerance of the illuminant locus. If
the color is extremely unlike an illuminant, then the CRI may
- The Television Lighting Consistency Index (EBU TLCI-2012) is a
similar measure of spectral quality, but oriented towards
Television camera usage, and using a more modern evaluation
criteria compared to that used by CRI95.
- The spectral graph may also
be of interest when comparing illuminants.