Quote Originally Posted by mrnobody
A CD spectrometer

As we can see from thees pictures the MEtal Halide has the most complete spectrum.

Interestingly the suns position in the sky changing the spectrum. So when the sun highers or lowers the spectrum changes and the plants react in a different way. Makes you realise that light movers are also something to be dialled into the next grow room.
The main purpose for a light mover is to spread the light around - think of chlorophyll as a solar panel+battery all in one. You can only charge the battery so far before it just won't take any more, so you move the energy source elsewhere until it can use that light again.

And it's not the spectrum of the sun itself that changes, rather the atmosphere filters out differently due to the angle at which it hits the atmosphere - we know this property as Snell's law.