1. Manually set audio sensitivity.,
Many HD DSLRs are set for automatic gain. Automatic gain works by boosting the power to the mic’s preamp, kind of like the ISO boost you often run into when using auto-exposure compensation on a still camera. Just as an image shot at a high ISO will show pronounced chromatic and luminance noise, high audio gain can lead to very noise-laden sound with a lot of anomalies. Depending on your camera, you may be able to disable the automatic gain or make other manual sound adjustments. Familiarize yourself with your camera’s options and experiment with these audio settings.
2. Choose your environment carefully.
The reason for automatic gain in the first place is that sound levels in the real world aren’t consistent, so for the best audio it’s important to learn the limitations of the onboard mic and to act accordingly. By planning ahead, you even can choose to avoid shooting in situations with a lot of ambient noise. Avoid areas or scenes where there are a lot of people or traffic, for example, and always have a windscreen with you, which will come in particularly useful when working in open areas or on beaches. Shooting indoors or in a controlled studio often will give you the best results.
3. Zoom with your feet.
The mic in a still camera captures the audio being produced close to the camera, so by moving the camera closer or farther away from the source, you can control the sound pickup to a certain extent. By getting closer to the subject, you’ll increase the signal-to-noise ratio for louder principal sound and pick up less background noise. This is why filmmakers often will place a handheld boom with a microphone just outside the frame of a scene. This also means that you should include a good wide-angle lens in your toolbox so you can be as close to your subject as possible.
4. Review your audio.
An essential sound recording feature lacking from all current HD DSLRs, unfortunately, is the ability to review audio through headphones as it’s being captured. That’s a shame because it’s very easy to miss background noise that can ruin the delicate sound in a scene. When recording dialogue, for instance, you may discover that an airplane flew overhead or that an air conditioner turned on in the next room. Even the inner workings of a refrigerator can be missed easily only to show up as an underlying hum through your captured audio. If possible, download your video to a computer and review your audio by playing it back and listening to it through headphones before you call a wrap on your shoot.
5. Use an external microphone.
The mini-jack on your DSLR is there for a reason. By adding even a basic, no-frills microphone, you’ll be able to record cleaner audio with less background noise while also avoiding the tendency of the camera’s onboard mic to pick up the sound produced by the mechanical workings of the camera and the lens. Thankfully, there are plenty of microphone options for working with HD-capable DSLRs, and there are even devices from companies like BeachTek, juicedLink and Sound Devices that allow you to use XLR mics and other professional audio equipment with a DSLR while also overriding the automatic gain.
CURRENT HD DSLRS lack the professional XLR audio input of dedicated video camcorders, but most video-capable still cameras do include a 3.5mm stereo jack (also called an 1/8-inch mini-jack). Although most high-end mics feature XLR plugs, you can find plenty of microphones with stereo jacks and, by plugging in, you’ll gain far more control over incoming audio. (You also might look for XLR-to-mini-jack connectors.) Here, we classify microphone types by their pickup patterns. Seen in diagram form, the various patterns show how the mic will capture sound from different directions. To choose the appropriate microphone for your shoot, first consider what you’re going to record.
Omnidirectional microphones, as the name implies, pick up sounds from all directions equally. For filmmaking, omnidirectionals normally aren’t a good choice because they pick up too much unwanted sound. Of the directional types, cardioid mics are popular for capturing dialogue and doing interviews. Their distinctive pickup pattern is roughly heart-shaped—hence, the name—which indicates that they’re most sensitive to sound that’s on-axis in front, becoming progressively less sensitive to peripheral sound and, ultimately, least sensitive to sound that comes from directly behind.
Hypercardioid, or shotgun, micro-phones have a pickup pattern that looks like an exaggerated, forward-facing cardioid shape; these models are among the most popular for HD DSLR shooters. Shotguns capture audio in a relatively narrow angle of view that’s directly on-axis. An inexpensive shotgun mic represents a good choice for most people who are starting to experiment with filmmaking or just recording motion clips.
You may have heard that lavalier mics are a necessity for capturing motion shots that involve people talking. Lavaliers are distinguished by their miniature size, not necessarily their pickup pattern. The most popular lavaliers are omnidirectional and are frequently hidden within folds of a garment, such as behind a tie, scarf or suit-coat lapel. You need to be aware of rustling noises and keeping wires and wireless transmitters out of the shot. Lavs are also available with other sound patterns.