Using The Eyepiece Cover - Canon Rebel T2i EOS 550D Instruction Manual

Remote Switch RS-60E3 (Sold separately)
This remote switch has a 60 cm/2.0 feet cord and enables you to press
the shutter button halfway or completely. It connects to the camera's
remote control terminal.

Using the Eyepiece Cover

If you take a picture without looking at the viewfinder, light entering the
eyepiece can throw off the exposure. To prevent this, use the eyepiece
cover (p.23) attached to the camera strap.
During Live View shooting and movie shooting, attaching the
eyepiece cover is unnecessary.
Remove the eyecup.
1
Push the bottom of the eyecup
upward.
Attach the eyepiece cover.
2
Slide the eyepiece cover down into
the eyepiece groove to attach it.
Remote Control Shooting
205