What is a good volume reference for the foley and FX editors to go by? I want to avoid having to re-adjust volumes of the various layers (DIA, Foley, and SFX) when I put all the tracks together for the Master.
Editorial calibrated to -18 or -20 dBFS = 85 dB SPL, Dialogue should be hitting a LM100 at -27dB LEQ(A) or -24 via a Stereo Phase Scope (but still about -27 when monitored via a Center channel Phase Scope if you're running a 5.1 mix bus - the -24 is due to a +3dB in-phase summing thing) - which when the room is calibrated to -18 or -20, should sound loud, robust, but comfortable.
To make sure everything translates to the stage properly we want to cut at the same calibration the stages uses, also since monitoring level affects our editorial judgements (both in terms of sound 'impact' and the Equal Loudness curve).
Sorry to disagree with Stavros, but in my humble opinion, it really depends on the room - 85 as a dolby reference is intended for rooms with a volume of 150 cubic metres or bigger. In a typical edit suite in the near field, you wouldn't normally want to monitor any higher than -20dbFS = 79dbSPL IMHO. Anything louder and you'll probably be under-cooking your balance for the stage or driving yourself deaf... If you get your monitor level right you shouldnt need to look at the meters.
Excellent explanation Steve. I'm going to second Brent on SPL according to room size, but it is a great response otherwise. I've got a break down on the recommended SPL level vs. room size in a post I did about monitor calibration on my site, Jellan. You can check it out here.