In 1975, Stanley Kubrick famously lit scenes in
Barry Lyndon only by candlelight. To do it, he had to use triple-wicked candles for a bright flame, push the only filmstock at the time to 250 ISO and acquire a super-fast T0.7 Zeiss designed for NASA (he had an old Mitchell camera chopped up just to work with this lens). This allowed Kubrick to shoot under a keylight of just three footcandles.