Watching the commentaries on classic Doctor Who DVDs I find myself learning an awful lot about the technical details of the show. Sometimes I come across the answer to some odd question that I've always wondered about, but never known how to find the answer for.
This week's revelation is about single-camera filming versus multi-camera filming.
I've often wondered why directors don't ALWAYS film with multiple cameras. By filming the same scene simultaneously from several different angles, wouldn't that reduce the amount of time needed to film the different scene elements? Wouldn't it reduce continuity errors?
Multi-camera shooting certainly IS faster, and it DOES make doing continuity a little easier -- requiring continuity checks only for re-takes of entire scenes, as opposed to whenever a scene is shot from a different angle. Another benefit of multi-camera shooting is that foley work becomes less necessary; everybody's voices and movements naturally sync together, instead of needing to be spliced up in an editing room later.
But these Doctor Who commentaries have given me insight into the NEGATIVE aspects of a multi-camera shoot...and there are a lot of them.
First off, there's the obvious drawback of needing to hire and coordinate several different cameramen. The actors also need to know their lines better, as there are fewer opportunities to check the script. Multi-camera shoots are by necessity more "theatrical" -- everyone in the right spot, everybody blocked out, all hitting their cues exactly -- which means that scenes MUST be rehearsed beforehand. This is a time commitment that might negate the time saved by shooting with multiple cameras.
More important, however, are concerns of lighting and sound. When you're only filming with one camera the director of photography can set up the lighting of each shot individually, paying close attention to those aspects of cinematography which make films look so much better than television programs. The boom operators can likewise record each shot in an optimal way, without needing to worry about actors wandering around the entire set and getting out of range.
But when you shoot with multiple cameras, the lighting is compromised: it must be adequate from every potential camera angle. And boom operators need to cover everybody no matter where they end up, instead of focusing on a small segment of dialog which must be recorded.
Finally, it's difficult to do really nice, elaborate close-ups of characters when multiple cameras are involved, for the obvious reason that the camera doing the close-up would become visible to all the OTHER cameras. This is one reason why fight scenes in the old Doctor Who tended to be filmed with single cameras, allowing tighter shots and therefore making it all look more tense and action-packed.
Nowadays it seems that multiple-camera techniques are rarely used except when a big, one-time-only practical effect is being shot, or when filming in front of a live studio audience. Otherwise, for reasons of lighting, sound, and general flexibility, single cameras are most desirable.