Secondary light source...

[Carter]

Someone explain this crap to me.

--Carter--

[Tony Moore]

well, typically, it's used to add some form to shadows.

I you have a setup with strong lighting coming one direction, you can add reflective light (that is, light from the main source reflecting off surrounding objects to illuminate shadows, etc) or even another less prominent light source (that's why it's secondary) to illuminate the shadowed areas from another direction.

the result is a strong light coming in one way, leading to a core shadow, and then some more weaker light.

typically, for contrast's sake, when in color, the secondary lighting is another color than the main lighting.

it's generally a good idea, as it helps to really define forms, whether you use it subtlely in more standard lighting situations, or not so subtlely in more dramatic high-contrast situations.

-T

[Dash Martin]

Yeah, what he said. If you want to see a secondary lightsource in action, hold up your forearm. On one side there's a blueish light which is coming from your monitor and on the opposite side of your arm, a white light from the room's lamp or whatever you use to light the room. Take not of the darker, shadowy area that seperates the two.

[Inkthinker]

It takes time to master, and a lot of practice... but if you can get it, your work will look ten times better.