I'm still not 100% clear on what exactly chromaticity is. Can someone explain?
This slide 35 from last lecture defines chromaticity as the intensity independent component of a color.
I may be wrong here. But I understood chromaticity to be a combination of the hue and the saturation part of HSV space. The V is the luminance that is intensity dependent and the other 2 are intensity independent.
@kapalani: Thanks for the answer. In HSV, V stands for value, which is a measure of brightness. It can be confusing whether we're specifically talking about luminance or perceived brightness (lightness), so you should inspect the definition of the specific HSV space used.
Wikipedia has a pretty good treatment here: https://en.wikipedia.org/wiki/HSL_and_HSV#Hue_and_chroma (see section entitled "Lightness")