What Can Be Done with an On-Camera Microphone?
Shooting a wide shot from the back of a church and expecting the on-camera mic to record the wedding vows is just crazy. However, some useful things can be done even with an on-camera microphone:
– If all that happens within a shot is to establish a locale, for instance, and no principal dialogue occurs, then an on-camera mic may be okay. Such establishing shots give a pause or bridge in the ongoing action, helping to anchor placement in time and space. Such shots are helped by the sync between picture and sound that makes them seem more real. For instance, my students once shot a documentary about an artist who worked with large Magic Marker–style pens. Choice of a quiet location and use of a directional mic allowed them to pick up the sound of the marker on paper. The sound effect, especially its in-sync nature, added a real sense of being there for that scene. Hearing it as the only sound emphasized the lonely nature of the task of creating art; on watching the fi lm, the audience thought that if they could hear that sound, it must be quiet!
Feature filmmakers call this type of sound Production Effects, and they cut one or more tracks specifically for them. This is as opposed to ambience or backgrounds, which refers to general background sound of an appropriate space laid over a shot or, more likely, a series of shots constituting a scene. Ambience provides an aural space for the movie to live in, but production effects are potentially even more powerful because of their sync nature to the actual picture. In order to make an ambience seem more real, hard effects can be cut over the top of it on other editorial tracks, portraying particular events in the picture through sound. Foley effects, too—those made synchronously in a studio while watching the picture—have the same effect: sync sound sells. So feature films go to a lot of trouble to build a sonic environment that matches what you see in the picture: ambience, hard effects, and Foley may all play a role. Still, the cheapest route to obtaining the advantages created by all of these layers is often production effects, if they can be captured cleanly at the time of shooting.
– If a documentary subject can be isolated from others and shot in closeup, with the camera only two to three feet from the subject, then a high-quality, directional, on-camera microphone may do. This means limiting the shooting style in order to accommodate the method of sound recording, but it is effective. I (Tom Holman) made a short documentary for the 66th reunion of the Mt Morris (Illinois) High School class of 1936. The lunch was around a big table with lots of gabbing. While I shot that for coverage, I also arranged to take each of the 12 alumni into a quieter corner and asked them questions in close-up. The close-up shots provided not only a part of the picture coverage, but also the sound that was used as principal voice-over, covering the wider shots of the group at lunch. It worked because I limited the kind of shooting I would do in the interviews to being quite close up, not only in framing, but in actually being close to the subjects, so that I could capture decent sound.
– On a fiction film with good actors, it is possible to shoot the picture with accompanying bad sound just for sync purposes (called a scratch track) and then go back and shoot the lines again for sound only, with the camera and its microphone in a preferred position for sound recording. Called wild track , this method requires tedious work in postproduction to resync all of the performances in the wild track to the scratch track, but it is possible to do. A key to it is getting the actors to perform in much the same way for the microphone as they did for the picture.
– It is generally a bad idea to shoot MOS (for “mit out sound,” a term coined by early Hollywood sound recordists, who tended to be German), because even the on-camera mic sound may prove useful in postproduction, if for nothing else, then for a guide track as to exactly what was said. For scripted productions there are deviations from scripts that make looping or replacing dialogue difficult when there is no precise record of what was said. For documentary films, having some sync sound available instead of putting in a general ambience makes editing easier.
– The camera is a sound recorder too, and often the only one on the location. It can be used as a sound recorder only, with the picture just along for the ride, which may be used to document where the sound was taken. With the low cost of media, and decent sound recording quality, this option is potentially much better than using a separate MP3 audio recorder, for instance.
– Another problem with on-camera microphones on tape-based cameras is that the mechanism of the spinning drum that writes and reads the dense audio/video data on tape causes mechanical vibration that is inevitably transmitted through the camera body to the microphone and induces noise there. You might not hear this in a quiet room from two feet away, but if you put your ear in contact with the camera body, you will hear it. This noise is what the microphone hears, and various microphones are more or less isolated from their camera bodies to infl uence how much is picked up. In one case, the Canon XL-1 series, several accessory devices were sold in the aftermarket to isolate the microphone better from the camera body than the stock equipment and reduce the noise. This vibration is usually heard only in very quiet shooting situations, though.
– Louder camera noises can also occur intermittently with zoom lens motors and other camera functions. Because these relatively soft noises are located very close to on-camera microphones, they can be a real nuisance. The largest help for overcoming them is to space the microphone away from the noise source.
Excerpt from Sound for Digital Video, 2nd edition by Tomlinson Holman and Arthur Baum © 2013 Taylor & Francis Group. All Rights Reserved.