Clearing Up The Noise Part I: Shortfalls In Capturing DSLR Audio
Photographers develop a sense of visual acuity after years of experience; thoughtful composition, artistic light placement and an intimate knowledge of camera settings come only with practice. Sound engineers are no less particular when it comes to honing their craft, and all professional filmmakers know the importance of capturing high-quality sound. As Scott Diussa, Field Operations Manager for Nikon, states in his blog post, “If [the audio] doesn’t sound good, then people won’t pay attention to the awesome images and video you put together. These three pieces, photography, video and audio need to be treated as equals.”
Modern DSLR cameras are fantastic for recording brilliant, crisp, HD video. They are not fantastic for recording sound. This is true for five main reasons: most HDSLRs (as of March 2011) employ consumer-grade automatic gain control (AGC), they don't capture great sound in the first place, they pick up sounds from the camera such as image stabilization and focus adjustments, they don't have XLR inputs, and sound can't be monitored when recording.
1. Automatic Gain Control
AGC may not be a problem if you are filming your kids in your living room, but for most filmmakers creating video for an audience, it is something that needs to be overcome. Auto gain works to level out sound irregularities by boosting quiet audio and diminishing loud audio. This poses problem when there are periods of silence, as it boosts unwanted ambient noise. As with focusing, strive to gain as much control over your craft as possible; you wouldn't want to rely on autofocus when an actor steps onto the set, and you shouldn't rely on AGC to choose what sound to include when you're interviewing someone on location.
2. Poor Internal Microphone QualityIn addition to employing AGC (which can't be turned off on most DSLRs today), the camera's internal mic can't be expected to meet your recording needs for the same reason a kit lens can't be used for sports photography: different situations require different solutions. Even if their was a one size fits all mic, the internal mic isn't high quality even for the most basic occasions.
3. Unwanted NoiseBecause the microphone is internal, it picks up the smallest sounds from the camera. Adjusting focus, focal length, and even the lens's image stabilizing adjustments will be picked up by the internal mic.
4. No XLR Connections High quality sound can be lost on its way from a microphone to the recording device; this is why professional cameras have XLR connectors built-in. Professional microphones can be plugged in directly to the camera – a feature lacking in DSLR cameras.
5. Can't Monitor Sound
DSLRs today also provide no way of monitoring sound, so noises that you might not even think of can ruin your audio – the breeze that picks up on an outdoor shoot or the air conditioner that kicks on won't be detected until everyone has packed up and gone home if you can't monitor the audio in real time.
While these shortfalls may seem significant, they can be overcome. In Part II: The Solutions, I cover a range of solutions employed by professionals and hobbyists for capturing usable sound.