How to Mic a DSLR Video
Poor audio quality is the first thing clients or critics will notice when watching your video. In this post, we discuss the choices you have in miking videos.
Shure Contributors: Thomas Banks, Chris Lyons, Gino Sigismondi
Consider this: On YouTube alone, over 60 hours of video are uploaded every minute of every day. More video is uploaded to YouTube in one month than the three major television networks combined have created in the past sixty years. The 51-second shot-in-a-dorm-room "Harlem Shake" garnered 36 million shares last year. There are other equally staggering stats, but one fact emerges: thanks to advances in technology (especially smart phones) more and more people are shooting videos. And many of them, nearly 15 million or so, have purchased DSLR (Digital Single Lens Reflex) cameras in the past year.
For a growing number of consumers, the DSLR's video function has rendered the camcorder obsolete the same way smartphone cameras have replaced their digital predecessors. We could devote a whole post to the pros and cons of camcorders and DSLR cameras for video, but we'll save that for the video experts. And besides, any shortcomings that DSLRs presently have - bulkiness, limitations in video recording time - will probably be addressed by manufacturers in fairly short order. We'll keep our focus on audio.
Experts agree on one thing: poor audio quality is the first thing your audience, clients or critics will notice when they watch your video. One videographer puts it this way: "It's easy to fool the eye, but it's a lot harder to fool the ear." Audio quality can make or break any video project. No matter how creative and professional the visual aspects of a production may be, these qualities can be completely negated by lackluster audio.
In this post, we'll discuss the choices you have in miking videos.
Start with Mic Basics: Dynamic or Condenser?
Microphones are basically transducers, or devices that take one form of energy, in this case acoustic energy, and convert it to an electrical signal that can be digitized. There are two types:
Dynamic – a very simple device that is rugged and reliable. Dynamic mics (like the SM58®, for example) don't require an additional source of power to operate but they can be somewhat limited in their sensitivity, so it's especially important for the sound source to be very close to the microphone. They also tend to be larger than their condenser cousins.
Condenser – these microphones use a different operating principle. They require an additional source of power ("Phantom power") that can be supplied by a battery or the next device in the audio chain. They are highly sensitive and tend to be a little more expensive than dynamic mics but are often preferred in recording applications. Condenser mics, in spite of rumors to the contrary, are just as durable as dynamic mics.
Flat or Shaped Frequency Response?
Making the right choice here depends on what you're recording. A man on the street interview or a musical performance?
A flat response means that the microphone is equally responsive at all frequencies. It will give you the most accurate sound and a wider frequency response. It's most common with condenser microphones. You'd probably choose this frequency response if you're recording a string quartet, because it will give you all the low end and the sparkle you need for a natural sounding recording.
A shaped response is more indicative of most dynamic microphones. If you're miking a human voice, a shaped response will give you everything you need to capture those frequencies.
Omnidirectional or Unidirectional?
A mic's polar pattern explains how it responds to sound coming at it from different directions.
Omnidirectional mics are sensitive to sounds coming at it from any direction. The benefit is that you don't have to worry about aiming the microphone. The downside is that it doesn't reject sound.
Unidirectional mics can be especially useful in video since they can be aimed at a sound source (with precise degrees of coverage) and away from undesired sound sources.
There are three types of unidirectional microphones: cardioid, supercardioid and hypercardioid. A shotgun mic, which we'll get to in a minute, is an extreme version of a unidirectional mic with a very narrow lobar pickup pattern.
Here's a reminder from Gino Sigismondi: "There is no such thing as microphone reach. They don't go out and grab sounds and bring them closer to the microphone. There is no zoom feature on a microphone. There's a 6 dB drop in level every time you double the distance. So if you move the mic from 6 inches away to 12 inches away, you've lost 6 dB on signal level." Whatever and however you're shooting, keep the microphone close to the sound source.
Camera mounted, Handheld, Wireless, Lavalier or Shotgun?
Creating good audio can be a real challenge when shooting video, especially if you're using a DSLR with a built-in microphone. These mics are not designed for high-quality audio. They are designed for sound sources that are very close to the camera (for instance, the operator) and they can pick up a lot of operating or background noise. Think back to home videos in your childhood. Whose voice did you hear as Dad or Granddad panned the landscape trying to get the excited squeals of the family at the Grand Canyon? Dad's. Granddad's.
The message here? Keep the microphone on the subject. Adding an external mic – a handheld, lavalier (also called a lapel) or a shotgun mic – gives you what matters the most: the best signal-to-noise ratio.
There are trade-offs and differences in cost, so let's look at them one at a time.
In this case, you'll be placing a lavalier mic about six to eight inches below the speaker's chin. They are generally clipped to a pocket, lapel, or necktie.
TYPES: The most common polar pattern is omnidirectional though unidirectional types may be used to control excessive ambient noise or feedback problems. Condenser mics are generally preferred.
- Don't allow speakers to touch the microphone or cable.
- Use a windscreen with mics to reduce plosives.
- Keep the distance from transmitter to receiver as short as possible. If dropouts occur, try moving the receiver.
- Make sure that the receiver's antenna has a clear line of sight to the transmitter.
- Mics can also be clipped to the collar of a shirt or blouse. Sound quality in this position may be somewhat muffled, because some high frequencies (which contain consonants) do not fully wrap around to the area under the chin.
- Make sure you have fresh batteries. Put them in right before the shoot and test them to make sure they work.
The most common kind of microphone for general use is the handheld type. This is more typical of the man-on-the-street interview. A good quality handheld mic should have an internal shock-mount to minimize handling noise and rugged construction to withstand physical abuse.
Handheld mics can be wired or wireless. Wireless mics come in two versions: a wired mic that can be converted into a wireless using a plug-on transmitter or a wireless handheld mic with the transmitter built into it.
Omnidirectional or unidirectional, generally dynamic. For newsgathering where the mic may be pointed back and forth between interviewer and subject, omni mics are the most common. A single on-air subject may prefer to use a cardioid to reject background noise.
- Use omni whenever possible.
- The microphone should be positioned about 6"-12" from the talker's mouth. Pointing the mic at a 45-degree angle will reduce the p-popping of plosives. This way, the breath blast goes past the mic instead of directly into it.
- With unidirectional microphones, holding the microphone very close (3"-6") will cause additional emphasis of the lower frequencies (known as Proximity Effect), resulting in a warmer, bass-heavy sound.
Shure option/cost: SM63LB omni dynamic mic ($180)
This mic is named for the long, slotted interference tube in front of the microphone cartridge that makes it resemble a shotgun. This tube helps reject sounds coming from more than about 30 degrees off to the sides, while still picking up sounds from the front. But let's talk about what shotguns mics are not: They are not telephoto lenses for sound. They do not allow you to zoom in on a conversation from 100 feet away.
Because a shotgun mic is either mounted to a camera or a boom, the viewer rarely sees it. In practice, a shotgun microphone can typically be placed at four to five times the acceptable distance for a standard omnidirectional microphone. But keep in mind that the shotgun mic will also pick up sounds coming from behind the subject.
All shotgun microphones are condenser types with a special lobar pickup pattern.
- Shotgun mics can be positioned slightly above, below, or to the side of the sound source, so that the mic doesn't appear in the camera frame.
- Try to avoid aiming the mic at a hard surface, such as a tile floor, brick wall, or hard ceiling. These surfaces reflect sound waves, and may reflect background noise into the microphone or cause the sound to be slightly hollow. (A heavy blanket can be placed on a reflective surface to provide some temporary sound absorption.)
- Shotgun mics are more sensitive to wind noise than standard microphones, so try to avoid moving the mic rapidly and use a foam windscreen if possible. (Larger "zeppelin" or "blimp" type windscreens are usually necessary outdoors.)
- Use a rubber-isolated shock mount to control handling noise that may be transmitted through a stand or boom.
- If you're using a boom for a scripted video, make sure your boom person has a script. If more than one speaker is going to be miked, the boom person needs to point the shotgun at the right person at the right time, a challenge when the mic needs to remain out of frame, the sound has to be consistent and the boom may be over 20 feet long.
These external camera-mounted microphones can run on AA batteries and have become increasingly popular with videographers. Since they mount directly on top of the camera, handling and motor noise is practically eliminated, and the lobar pattern of the condenser shotgun mic rejects off-axis sound. Since the short shotgun mic is attached to the camera, there's no need for a boom operator.
In addition, some models feature onboard digital flash audio recording and are capable of recording up to 10 hours of audio on a sound card.
- The camera operator should be aware that the rear lobe of the polar pattern can pick up some sound from the rear.
- Shotgun mics do a great job of picking up frequencies in the vocal range, but they may not be the best choice for recording musical instruments.
- Use a windscreen to keep wind and drafts of air out of your audio. Effective wind protection is mandatory in outdoor environments.
- Use the mic's low-cut switch to filter out undesirable low-frequency sounds that can detract from your audio.
- Use a shock mount designed specifically for the camera-mounted shotgun you're using.
Shure option/cost: VP83F LensHopper™($349)
Now that we've laid out the most typical options, it's time to ask yourself these questions:
- How many people am I miking?
- Do I want the mics to be visible? Is someone available to operate a boom or monitor sound?
- What kind of budget do I have?
- How will my needs change in the next year?
Your situation will dictate which of these microphone options make the most sense for the type of DSLR video you're shooting. According to Thomas Banks, "you're going to encounter some compromises right off the bat unless you have an unlimited budget". A corporate rig is likely to be different than the 'step-up from my iPhone' YouTube project you may have in mind. The good news is that there are camera and mic solutions for every step along the way from entry level to indie film.
For more information on the subject: Download the Shure Audio System Guide for Video and Film Production
Also check out the How to Get Better Audio for Video (below) and other topics in the Shure webinar archives.