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Viewfinder: External Microphones

Viewfinder: External Microphones

Most camcorders have a built-in mic, which is very limiting. A camcorder's zoom function brings the visual information closer, but zoom functions for microphones have technical limitations.

The zoom function on a camcorder works well when used to bring the visual information closer to the camcorder. An optical zoom works better than digital zoom because it uses a optical lens that is adjustable between wide-angle and telephoto. A digital zoom crops the image and magnifies the result of the cropping through a process called interpolation resulting in a loss of image quality compared to an optical zoom lens. In some cases, the loss of image quality is negligible. Using the zoom in telephoto setting brings the visual information closer to the camcorder effectively. There have been attempts to do the same with audio information, but none work as well.

Bringing the audible information closer to the camcorder is more challenging. The equivalent to a telephoto lens is a microphone that is highly directional, capturing the acoustical information (the sounds) coming from the area directly in front of the camcorder. The inner elements of a microphone are the primary source of differences in directivity. A microphone's directionality or polar pattern indicates how sensitive it is to sounds arriving at different angles about its central axis. The equivalent to a zoom lens is a mic which is continually adjustable between omnidirectional and unidirectional. Due to a variety of technical limitations, a zoom mic is much more difficult to design compared to a zoom lens.

Some camcorder manufacturers include up to 4 microphones on a single camcorder. When all 4 are in operation, the result is omnidirectional, when just two are used, along with some fancy software, the result is unidirectional. The reality is that most camcorders have just one built-in microphone and this is a limiting factor. It is best to use an application-specific designed external mic. For example a lavalier microphone is made for hands-free operation. These small mics are worn on the body. A unidirectional shotgun mic is another choice and it is mounted on the camcorder. However, in order to use these application-specific designed external mics, the camcorder must have a mic input which is usually a 3.5mm jack. This simple little feature is often all too elusive on many camcorders.

I am sure that the cost for manufacturers to add this feature is less than a few dollars, so some may ask why it is so often omitted. The reason is that this feature is included on higher priced camcorders as a method of distinguishing it from more basic camcorders. Manufacturers with a broad line of camcorders will exclude a mic jack on camcorders costing less than a few hundred dollars. However Kodak, a recent newcomer to the camcorder-manufacturing field, is bucking this trend. They do not have a broad line of camcorders so they are offering the 3.5mm external mic jack on their $140 camcorders. Finally, we starting to see external mics being used with low end camcorders.

Matthew York is Videomaker's Publisher/Editor.

Tags:  January 2011
Matthew
York
Sat, 01/01/2011 - 12:00am