Generally for lighting circuits if you ran 8 AWG strictly for voltage drop reasons it would not be on a 50 amp breaker, it would be on a 20 amp breaker.
If 8 AWG supplied by a 50 amp OCPD was specified it is because they want to load the circuit heavy with fixtures. This of course would be counter productive as far as voltage drop and of course a single circuit failure will darken a large area.
[This message has been edited by iwire (edited 09-29-2006).]
