Magic Lantern greatly extends the capabilities of our Canon T2i cameras. To install it, begin by downloading it from here. Before you can install Magic Lantern, you will need to have Canon's Firmware version 1.0.9 installed. It can be downloaded here:
Steps to install Magic Lantern:
unzip into a folder on your computer (or directly onto the root of your SD card)
copy the files (NOT the .zip file) onto the root of your SD card.
Make sure that your SD card contains the files 'autoexec.bin', 550D-109.fir, and a folder entitled 'ML'. It won't work if the files are in a Magic Lantern folder - they must be on your SD card when you first open it! It should also contain a 'DCIM' and a few other photo folders.
Steps to make your card bootable:
Set the camera to M (Manual)
Click the 'Menu' button
Scroll to the far right (3rd wrench)
Scroll down to 'Firmware Ver.' and click the 'SET' button
Select 'OK' and click the 'SET' button
Wait patiently. It will take about 15 seconds. You will see a few screens go by before the 'SUCCESS' screen appears (green letters).
Restart the camera
To run Magic Lantern:
Turn the camera on (OK I guess that's a little obvious)
Switch to 'Movie' mode (top dial)
If the Magic Lantern display is not active, push the 'DISP.' button (you may have to push it more than once as it cycles through the 3 viewing options)
To open the Magic Lantern menu, push the garbage can (bottom right of camera)
Go to Audio and set Analog Gain to 17 or 20 dB
Check your input Source and set it appropriately ('external stereo' if you are using a boom pole and shotgun mic)
Check and confirm the audio meters!!! If you have no meters, you have NO sound.
Check to make sure the audio is high enough, but not clipping (yellow or red)
After you've finished a project:
use the camera to format your SD card
if you format from within the Canon camera menu, it will keep Magic Lantern