http://www.creativepro.com/article/inside-photoshop-the-color-lab
Recently I started using LAB color sliders in photoshop to pick colors instead of HSV just for the hell of it. And I
started getting curious as to exactly what the hell LAB was, being the color nerd that I am. Though I'm also very
lazy so I never bothered to research it...
Then while browsing good ol' DA I came across Janaschi's journal post... and it's very clear from the examples that LAB blends colors better than standard RGB or CMYK. And that's where I found the link I just posted.
So in short, basically while CMYK uses the primary colors of ink, and RGB uses the primary colors of light, LAB treats colors the way the human eye does (Lightness (rods), (a)green+red, (b)blue+yellow (cones)) and therefore has a complete spectrum of colors visible to humans whereas the other systems are limited. Also, LAB can be converted to CMYK for printing without the color discrepencies that RGB to CMYK does.
In the realm of digital painting, it actually causes the colors to blend differently, since luminescence is treated separately from color. So yeah, seems pretty cool, I'll be experimenting to see what happens.
EDIT: This just in... LAB mode ROCKS MY SOCKS OFF.
It's like painting with a lightweight dodge and burn that doesn't destroy the colors. *_* And the blending is
so smooth it's unbelievable... I'm not getting those weird pixelly dark spots anymore. (in my research I have
discovered that 8-bit RGB blends subtractively, hence the dark spots...) You can't save jpgs in LAB, but I
don't effing care. It's wonderful to work in.