Originally posted by Digitalis due to the light absorption of air, it's impossible to make a lens faster than f/0.5 and the adapters that he used to make that 50mm lens in to a 36.6mm lens actually made the lens slightly slower, not faster and it certainly didn't do wonders as far as it's handling of chromatic aberrations.. Kubrick actually push developed the film for the candle lit scenes to the best of my knowledge the fastest cine film available in the early to mid 1970s was about ISO 500 and he pushed it to ISO 1000 so, ISO 3200 with a 50mm f/1.2 works out to roughly the same exposure on a 50mm f/0.7 give or take a 1/3rd of a stop.
Nice. I didn't know that!
Though, I'm not convinced with f/0.5 being the fastest possible aperture. The F-number just expresses the ratio of focal lenth and pupil diameter. Unless air significantly affects the focal length, I don't see where it would fit in this equation. And even if it did you'd have to take into account air pressure and temperature then (which in turn would mean that in vacuum a faster aperture would actually be possible).
Anyway, getting off-topic