Canon Rebel T2i Quick Start Manual page 79

Option Two: Small directional microphone
The Rode microphone is small
mono directional microphone
that can be mounted directly on
the camera.
It picks up sound from any source
that is directly in front of it and
minimizes sounds from the rear
and sides of the microphone (a
super-cardioid polar pattern).
Point the microphone at the
mouth of the speaker.
Because the camera is mounted
directly on the camera it can pick
up any noises from operating the
camera.