How dark is it on Titan?

[Colophon]

Looking at the pictures from Huygens, I was wondering what sort of exposure is needed (OK, it's probably not "exposure" in the traditional sense, as I don't know what sort of imaging device it uses). Titan is a long long way from the sun, and has a thick atmosphere, so how much ambient light is there at the surface? Is reflected light from Saturn an appreciable light source?