http://www.silverblades-suitcase.com/tutorials/htm/48.html
For those interested in such stuff 
note as I say in it, that render settings for max effciency vary a lot on each shot/type of scene of course, but should be very useful for you.
Really would need to sit down and compare a bunch of different scenes in detail, but don’t have time, patience or resources at moment.
Sorry for typos: it’s free ("don’t look a gift horse in the mouth" and all that), I’m sick and have more imortant things to worry about that lexicological disasters, so you know where you can stick any complaints about my typing, hehe 
