"star light star bright first star i see tonight" :3

I imagine that you dont need as much light to get a good picture with lens like that given its greater viewing angle, should help it collect more light I would think.

possibly yeah

Ah well, might make for an easy nerdy experiment XD With a stationary camera utilizing identical settings in both instances. Take a picture with the fish eye and one with a standard lens. If the standard 18-55mm or whatever, shows up as darker, then you know to reduce the time or aperture when using the fish from what you would normally expect. Traditionally, in accordance with optics, its the aperture that determines the amount of light that enters into the lens and thus the sensor (hence why telescopes and IR cameras need HUGE apertures). Now I would think that a lens that bulges more convexly would have a similar effect, especially if the lens projects past the hood of the lens, more surface area to redirect light in effect.