The very first thing to learn about working with audio is that it can be as straightforward or as complex as you want it to be. The microphones built into HD DSLRs are a convenient audio source for photographers just getting started with video on their still cameras. These internal microphones are similar in many ways to a basic kit lens. They’re designed not for professional use, but rather to offer an audio solution that gets workable results while keeping the body of the camera comfortable to use and compact enough to carry. This also means that these onboard mics are fairly limited in their capabilities. With that in mind, there are a few different tricks that can help you to capture above-average sound.
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.