DLSR's are becoming more and more powerful and with this power comes new capabilities. This new power has made it possible for Manufacturers to integrate HD video recording turning them into HD-DSLR. These new devices are becoming better and better at capturing great video, however, the one thing that has not changed much is the poor audio performance of these cameras. Given that HD-DSLR'S are primarily imaging devices, the audio portion of the hardware is often under emphasised and sometimes even overlooked.
The overwhelming majority of HD-DSLR's have very poor on board microphones, kind of like the "very basic" lens that comes packaged with many camera. Most knowledgeable users realise that the limiting factor of the camera is the "basic" lens it came with and will immediately set aside this lens in favour of a much better one or a variety of lenses that are often worth as much if not more than the camera itself and all this for very good reasons. We will also purchase an external flash, stands, filters, etc. all in the interest of creating the best images/video possible.
With video however comes another equally important component that we need to consider, AUDIO!
The internal microphones on most HD-DSLR's are basically pinholes with minuscule microphones inside.
These minuscule microphones have extremely limited capabilities. If you plan to do any video at all, it is extremely important to consider the purchase of an external microphone that is suited for your application.
There are many options available to you; the following is intended to demystify this for you without getting into the fine details that are not necessarily of interest to a videographer.
Dynamic and Condenser Mics
There are 2 dominant categories of microphones that are of interest for video: Dynamic and Condenser.
Dynamic microphones are primarily used in live sound applications and are less sensitive than condenser microphones, this offers certain advantages in live music/presentation applications. They are also generally less expensive to manufacture. Condenser microphones on the other hand are primarily used in studio and broadcast applications because they are more sensitive, more detailed and offer significantly better overall sound quality, however they are generally more expensive to manufacture and require a power source. Most on board camera microphones are dynamic because they are cheaper to manufacture and do not require an electronic circuit to power them. All high quality camera mount microphones are condensers and require a battery to be used with HD-DSLR's.
Broadcast microphones are available in 2 variants: STAND ALONE and CAMERA MOUNT. Stand alone microphones typically used in broadcast applications or with high end video cameras as they usually require an external mixer, bulky cables and often a separate person to operate them which makes them impractical to solo HD-DLSR users. Camera mount microphones are the logical choice for the HD-DSLR user because they are compact, simple to use, discrete, mount right on your camera and do not require any external gear or another person to operate.
Microphones have a "polar pattern" which basically describes the area of coverage of the microphone.
There are 2 main categories of camera mount microphones that are available to you: Shotgun Mics and Stereo Mics.
There are 2 things that you need to have on your camera in order to be able to use any camera mount microphone:
Your camera must have an available shoe mount (where you normally mount a flash):
Your camera must have a standard 3.5mm microphone input jack.
Camera mount microphones do not use the electronic connections on the mount, they only use the attachment point top be secured into place. If you need your shoe mount for another device, there are a variety of adaptors that you can use to double up your shoe mount and use both devices at the same time.