Originally posted by Schatzi
Get yourself hidden in a gunnysack. Noone can *see* you in it... but you can see clearly through from close up (and the dark inside to the light outside).
To extrapolate: If you are enveloped within a cloud of smoke, the smoke is not only blocking a percentage of the light from illuminating you, it is also obscuring the target's vision with particles... if you are in the smoke cloud, your target is only being obscured by the particles, which are also perceptually farther apart than they are to the target... also the target is not light-dampening obscured.
The perceptual part might seem confusing, sorry, trying to think of a worthy analogy.