Tuesday, January 3, 2012
DPP Solutions: Go Wireless
Cut the cord to improve the audio when you’re shooting HD video with your DSLR
|This Article Features Photo Zoom|
Most HD video DSLRs have the ability to deliver superb, broadcast-quality images. Yet anyone who has shot video on their rig may have been disappointed with the quality of the audio. Assuming your camera has an 1⁄8-inch audio input, one solution is to plug in an external microphone and place it on a stand or have an assistant act as a boom operator or even have your subject hold it to keep the mic near the action. However, consumer-style mics with 1⁄8-inch connectors are limited to a maximum cable length of about 15 feet, after which the signal becomes weak and susceptible to picking up hum and buzzing.
The Wireless SolutionWireless microphones are nothing new, having been in use for a half century. There's good and bad news here. The technology for wireless mics has improved significantly, becoming smaller, more reliable and more affordable, yet it's still the classic situation of you get what you pay for. High-end pro units can cost upwards of $1,000 per channel, but useable systems for a DSLR user begin at around $100. Yet pay a little more, and you can expect more features, higher-quality microphone elements and more robust build quality. The latter is hard to quantify, but on cheaper units that may be fine for occasional users, seemingly insignificant items like battery door covers, switches, knobs, controls and internal parts don't hold up to heavy daily operation.
The basic components in any wireless system include the mic element, a transmitter and a receiver. Handheld wireless mics that are often used by talk show hosts and rock singers incorporate a battery-powered transmitter and antenna. Approximately the size of a deck of cards, bodypack transmitters have a beltclip and an input jack for connecting an external headset or a lavalier mic. Standard in film work and worn on the subject's chest, the miniature lavalier mics attach to tie-clip-style mounts and are fairly inconspicuous. Wireless receivers come in many styles, but for DSLR use, look for a compact unit that can attach directly to your camera's shoe mount and has an 1⁄8-inch audio output cable compatible for interfacing directly to your camera.
Audio-Technica's entry-level ATR288W TwinMic wireless system includes a handheld and a lavalier mic for use with its beltpack transmitter.
Features And FunctionsBesides the physical form (small, lightweight, battery-powered, etc.), there are other features to consider in selecting a wireless unit. Systems with diversity operation transmit and receive two signals simultaneously, with the receiver automatically selecting the stronger of the two. This gives you more of a fail-safe operation, helps guard against momentary signal "dropouts" and increases the operating system's range. Another desirable feature is switchable transmission frequencies, so if interference is encountered on one band, the user can change to another frequency. Higher-end systems can scan the airwaves and automatically switch among hundreds of available frequencies. Other advanced functions include the ability to remotely monitor the battery life of the transmitter from a display screen on the receiver.
Tips, Techniques And Final AdviceSpeaking of batteries, modern wireless units are highly power efficient and often provide five hours of operation or more, but start your shoot with fresh, new batteries to avoid missing a great take. Also, wireless systems work best when used within line of sight, so try to ensure a clear pathway between transmitter and receiver antennas. On some shoots, I've attached the receiver to a pole or lighting stand and then used an 1⁄8-inch extension cable to connect it to the camera for improved reception.
A wireless mic adds a powerful new dimension to your DSLR rig, but if you're shopping for a system, try to avoid buying a used system. Not only do the latest models offer better performance and more reliability, but the pre-owned market is filled with units in the now-discontinued 698 to 806 MHz range—frequencies made obsolete by an FCC ruling two years ago and illegal for operation in the U.S.
George Petersen is a noted audio authority and Special Contributing Editor for HDVideoPro magazine's CineSoundPro section.