Stereo wireless hops have become a very important piece of gear in a good sound person's kit. This transmitter/receiver set allows the stereo output of the mixer to be sent wirelessly to the camera without the hassle of the sound mixer and camera op being tethered together. Some pros/cons and usages of a stereo wireless hop are as follows:
-PRO: Allows the multiple inputs of the audio mixer to be summed to a stereo mix and recorded directly on the camera.
-PRO: Provides freedom of movement to both the sound mixer and camera op whereas a breakout cable has a limited length and restricts movement. In tight, crowded situations this freedom of movement is critical.
-PRO: Allows for quicker post-production turn around because external audio files do not need to synced with the video.
-CON: Requires camera op to monitor the audio input on camera to ensure the receivers are working properly, the levels are sufficient, and there is no RF interference. The camera op needs to be focusing on the picture, not the audio.
-CON: A good stereo or quad wireless hop, such as the Lectrosonics D4 or Zaxcom Stereo Wireless Camera Link, is roughly $4,000 but a break-out cable is about $250.
-CON: Audio circuitry on inexpensive cameras degrades the audio quality. Cameras are intended to provide a nice looking picture, not high quality audio.
-CON: Audio is only recorded when the camera is rolling unless a separate audio recorder is being used.
Like many aspects of production work there are cost/benefit trade offs. As an audiophile I would, of course, love to see everyone use the audio from my Sound Devices recorder but I recognize that isn't always prudent. Post production time and budget will typically dictate which audio files are used in the final deliverable; on camera audio or external audio.
