If you have Cannon 500d you know already that it doesn't have a external mic jack. But you can add one within a couple hours.
XCFloresX photography does an awesome job of this mod on a youtube video. Watch his video first!
My instructions are just a specific case for my camera and the 3.5mm jack I chose to use. I have the Asian model not the Rebel.
Make sure you get all the screws out before you remove the back case. The back case comes off quite easy. My camera had a screw hiding below a sticker.
When you take the back cover off be careful not to damage the ribbon attached to the circuit board.
Small Philips screwdriver - make sure it fits properly in the head, these little screw heads will strip out easily.
Small Flat screwdriver - to pry off the back cover.
Hot Knife or a small saw, something cut plastic
Small file or Dremel
3.5 or 2.5 2 pole audio jack
Step 1: Placing the Jack
As you can see in the picture, the jack body is a little too wide to fit in.So I used a pair of bolt cutters to cut the material in yellow out.
Step 2: Soldering the Jack
Be careful cutting the internal mic wires. Allow your self enough wire to work and stip the wires. They are very tough to strip!
And I also bent down the jack tabs to ensue the back case would fit back on.
The back cover has a metal shield inside it so I added a small piece of electrical tape to ensure the jack contacts didn't short out.
Step 3: Back Cover Material Removal.
The yellow shows where I had to remove material from the back cover.
I used a hot knife to remove the plastic and then a grinder to remove small amount of metal required.
NOTE: Try not to get any small bits of plastic or metal into the body of your camera. Nothing good can come from that.
Step 4: The Test Fit
It took me 3 tries to get the cover back on and fitted properly.
Hint: I had plugged a 3.5mm male into the jack to help hold it in place while trying to get the case closed.
When it is done the jack made a very snug fit.
Step 5: Drilling a Hole in the Side Cover
Drill a hole in the side cover to just fit around the jack.
Hint: to get the hole in the right place:
put a piece of tape in the cover where the hole should be.
then align the side cover along the x axis and draw a line.
then repeat the procedure for the y axis.
where the 2 lines cross is where the hole center should be.
This hole needs to be very exact because there is no room for movement. measure twice and cut once.