Hola xandre31:
Yo tambien lo tengo entendido tal como tú dices, pero mira:

http://www.imdb.com/title/tt0072684/trivia

"Contrary to legend, this film did use artificial lighting. Artificial lights were used, for example, in the scene where Brian learns he's getting a horse. However, it is true that no artificial lighting was used for candlelit scenes. A lens built by the Carl Zeiss company for NASA, a 50mm Zeiss lens modified with the Kollmorgen adaptor used in still cameras, was used to shoot scenes lit only by candlelight."

Un saludo.