Sorry to bore on this but it is one of my bugbears (has any ever seen a bugbear - what does it look like, and how many legs?).
My (UK) company issues an instruction along the lines of "dimming" the lights for T/O & L but not to the extent that the cabin is in darkness. This strikes me as a triumph of compromise over common sense. It neither provides night vision nor sufficient light from alternative sources if things start going wrong and metal gets bent.
My vote says turn 'em off. When things go bad, the lights fail - the emergency light switch won't help you much either! If people have open retinas they can see what is going on when it all goes dark: Relying on a dubious power source for exit paths strikes me as somehat optimistic to say the least!
BTW shade blinds open so you can see what is merrily burning away outside (or not as the case may be)
[This message has been edited by TightSlot (edited 14 October 2000).]