An on-camera microphone is a special type of mic developed to run smoothly with a camcorder or a video-enabled DSLR camera. It is lightweight, able to mount to the shoe of a camera.
Reasons to use an on-camera microphone
The inbuilt mics on cameras often sound not good. They always pick up lots of noises produced by the camera itself. External quality on-camera microphones are designed to outperform the inbuilt ones. They tend to help improve the clarity of dialogue when subjects speak in front of the camera OR capture more natural environmental sounds.
Types of on-camera microphone
No type of microphone is ideal for every purpose. Typically there are two totally different shooting scenarios in the video: recording dialogue and recording environmental sound. If it is the recording of ambient sound, STEREO on camera microphone is a good choice. If it is the capture of the subject's voice in front of the camera, the SHOTGUN microphone makes it.
Shotgun microphone. It has a barrel-shaped construction and tends to be longer than a typical mic. It comes to have more reach than other kinds of microphones. As a directional device, it performs better when picking up human voices. This is why it is often used to pick up dialogue. It's notable that the shotgun mic should be positioned as close to the speaker's mouth as possible.
Stereo microphone. Similarly to the way human beings pick up sound, a stereo microphone does it using two microphones housed in the body. The two microphones then output separate channels of sound usually Left and Right. Still, stereo on-camera microphones deliver audio on a single stereo mini-plug connector. Obviously, stereo microphones are excellent at immersing the viewer in an environment.
Accessories needed when using an on-camera microphone
A shock mount may be necessary for the DSLR camera microphone. It offers basic protection from damages, though it is in fact designed to isolate mics from mechanically transmitted noise. An extension audio cable is also a good addition in some situations. However, proper wind protection is a necessity when the microphone for camera is used outdoors. Most microphones are shipped with a foam windscreen which is useful for light breezes or indoor air but does not perform well when there is a gust of wind. At this moment, a kind of wind protection, namely furry windshield comes. It works like a sock that can be pulled over the microphone for complete protection. All these are foundations to build the best camera microphone.