FEASA LED ANALYSER
FUNCTIONAL VERSION
Colour and Saturation
Figure 1: Hue (Colour) Wheel
RED = 0º
GREEN = 120º
BLUE = 240º
Colours can represented by a 360° degree circular Colour wheel. The three Primary RGB values
can also be represented as a single value called Hue. Hue is a measured location on a Colour
wheel and is expressed in degrees. For example, Red will have a Hue value near 0°, Green
will have a Hue value near 120° and Blue will have a value near 240°.
A pure Colour will be represented on the Colour wheel as a point near the outer edge. White
will be represented by a point near the center of the wheel. The degree of whiteness in a LED
will affect its position on the wheel – the greater the amount of white the closer it will be to the
center.
The Feasa Led Analyser output of Saturation is NOT part of the International System of Units.
and is not an absolute or traceable unit of colour measurement. It is part of the Hue Saturation
and Relative intensity (HSI) system of describing colour. The degree of whiteness emitted by
the LED is represented by the term Saturation. A Saturation value of 0% represents pure
White. A Saturation value of 95 - 100% represents a pure Colour such as Red, Blue, Green,
etc. It is a relative output much the same as the Relative Intensity output, and is used to
compare similarly coloured LEDs under test. The Saturation values are calculated within the
Feasa Led Analyser for each channel of the LED Analyser, relative to the LED under test.
There is a consistency in the Saturation readings between all Feasa Led Analysers, for LEDs of
a similar colour, in a similarly constructed fixture.
Usually the user must determine the Hue and Saturation values by testing a number of LED's
and recording the results.
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