But there is one area of d-SLR video performance that's sorely lacking: audio recording. The mics built into today's d-SLRs are fairly lousy. While digital camcorders offer multi-channel, surround sound recording or directional zooms (where the microphone will focus sound collection forward as you zoom the camcorder's lens), d-SLRs offer just rudimentary microphones.
That's no reason to cast down your camera in disgust, however. With a few accessories, ranging in price from under $100 to a few hundred dollars, you can outfit your d-SLR for true high fidelty audio recording.
External Microphone
The least expensive, least sophisticated way to get some high-quality audio into your footage is to use an external microphone. These mics can be mounted to the camera via the hot-shoe and connect via a 3.5mm microphone input. While they'll add some bulk to your camera, they will do a far superior job at recording audio than the built-in microphone. Be sure to purchase a mic with a windscreen, for, you guessed it, filtering out the wind. These add-on mics are particularly susceptible to wind noise as they're both more sensitive than internal mics and are more exposed.
Most d-SLRs offer very few controls over audio recording in general, so adjusting things like the levels of sound aren't an option, but you'll still get higher quality audio than you would otherwise.
External Recorder
If you want to get a bit more sophisticated, you can bypass the the camera completely and use an external audio recorder. An external recorder captures high-fidelity sound with its own microphones to another memory source (usually a SDHC card) and not your camera. An external recorder delivers a few key benefits. First, you can listen in to the sound you're recording using headphones, and there are usually external sound level readouts on the recorder's display.
Another advantage to an external recorder is that you can attach extra mics to an external recording. So, for instance, if you wanted to record an individual speaking, you could attach a lavaliere microphone to their clothing and get a very crisp sound saved to your recorder's memory. Some external recorders can be mounted directly onto a digital SLR as well, so while they add some extra bulk, it's not something else you have to lug around. However, other recorders are too large or not designed for mounting.
The downside to an external recorder is that, since you're recording sound to a separate storage format, you need to synchronize that audio with your video file after the fact. This isn't terribly difficult, software programs like PluralEyes use the sound recorded by the camera's microphone and syncs it more or less seamlessly with the audio file created by your recorder. However, it does take a bit of planning and additional investment in software. It also involves more work after the video-recording is done.
External Sound Adapter
If you're really serious about high quality audio with your d-SLR, you can spring for an external adapter. These typically mount to the bottom of your camera (using the tripod socket) and deliver a lot of the same benefits as an external recorder, with a few key differences. These adapters don't have their own microphones, so you will need to use either wired or wireless accessory microphones to collect sound. They do offer headphone jacks and level readouts and, crucially, they pass the sound directly into your camera. That means that you won't have to worry about any post-shot syncing, since both the video and audio are saved to the same source.
External adapters aren't cheap - they can run from $500 on up, and that's not counting the investment you'll make in microphones. They're also large - they can be much larger than an external recorder - and since they're mounted to the bottom of your camera, you won't be able to use a tripod simultaneously.