6
50
60
60
70
80
90
100
110
120
130
140
1
70
Fidelity Index, Rf
Gamut Index, Rg
80
90
100
2
2
1 Approx. limits for
sources on the
Plankian Iocus.
Increase
fidelity
Decreasing
saturation
Increasing
saturation
Approx. limits for
practical light
sources.
C.E.S. Color Evaluation Samples
Trade off Rf & Rg
Arte & Culto | The best lighting
Shining
with true light
The new TM-30-15 method
of evaluating colour rendering,
developed by the American
standardisers of the IES (Illuminating
Engineering Society), represents
a development of the CRI (Colour
Rendering Index) standard. This
new method is now used both by
professionals to choose the right
light source and by manufacturers
to develop new spectra for their light
sources.
Compared to the older CRI, which
still remains the reference standard,
TM-30-15 uses 99 CES (Colour
Evaluation Samples) – as opposed
to the CRI’s 15.
The 99 samples used in the TM-30 method were selected logarithmically from the
105,000 colours visible to the human eye.
By analysing the values, the TM-
30-15 method extrapolates an
evaluation consisting of the following
two parameters:
• Rf (where f stands for Fidelity,
colour fidelity) refers to the
average colour reproduction
fidelity value of all 99 CES
samples, with a maximum value of
100.
• Rg (where g stands for gamut,
colour extension) is used to
assess colour saturation; the
figure obtained can fluctuate
below (desaturated colour, up
to 60) or above (oversaturated
colour, up to 140) the ideal value
of 100.
