Canon Rebel T2i Quick Start Manual page 111

Clip-on Wireless Microphone
For a more inobtrusive microphone (or if
you require both hands), use the
Sennheiser AVX wireless microphone kit.
The clip-on wireless microphone should
be placed about 20 to 25 cm below your
mouth. It also gives a very close
"intimate" recording like the SM 58.
This is an omnidirectional condenser
microphone so it does pick up more
room noise than the SM 58. The pick-up
pattern is spherical.
Condenser microphones are more
sensitive. The speaker should avoid
wearing noisy clothing like squeaky
leather jackets or bead necklaces, etc.