## Colour space

It took me a while to get my head around the xyz colour space.  You start with XYZ which roughly resemble red, green and blue.  If you imagine this, because there are three values, you would need a 3d space in order to vie the correct colour.  This is just too complicated for most people to comprehend (according to some sources, even Stephen Hawking has problems visualising in 3d) so a 2d version was made.  This is called th xyY.  So, what really confused me was where does the z go?  It can’t just disappear.  Well, x+y+z =1.  So, if you know what x and y are, you can work out z whilst having the luxury of viewing it in a simplified way.  Easy, you see. Once you get your head around it.

This is the CIE 1931 standard observer colour space which was measured by 21 observers with a field of view angle of 2 degrees.This colour space is used widely throughout many industries including the stage lighting industry and by colour gel manufacturers.

Tallow candles have a chromaticity of x=0.534, y=0.412.  Of course, we can now work out what z is by 1-(0.534+0.412) = 0.054

The graph above shows the position of the LEDs and the tallow candle.  You can see that the candle lies on a line between the yellow LED and the white LED.  This means that using a mixture of yellow and white, it should be possible to achieve a colour match.  The tallow candle also lies within the three LEDs – Orange, Green and white.  This triangle is called a gamut and any colour within this gamut can be matched using the three colours.  So, this is especially useful for this project as if the candle starts to burn down and produce a more orange flame, these three colours will be able to deal with this.  Once is leaves the line between yellow and white, it will no longer be able to be matched with just those two colours so the three colour option might be necessary.