Canon EOS REBEL T4I Instruction Manual page 27

Manual Sensor Cleaning*
I_ While cleaning the sensor, never do any of the following. If the
power is cut off, the shutter wilt close and the shutter curtains and
image sensor may get damaged.
• Setting the power switch to <OFF>.
• Opening the battery compartment cover.
• Opening the card slot cover.
The surface of the image sensor is extremely delicate. Clean the sensor
with care.
Use a plain blower without any brush attached. A brush can scratch the
sensor.
Do not insert the blower tip inside the camera beyond the lens mount. If
the power is tumec off. the shutter will close and the shutter curtains or
reflex mirror may get damaged.
Never use canned air or gas to clean the sensor. The blowing force can
damage the sensor or the spray gas can freeze on the sensor.
If the battery level becomes low while you clean the sensor, the beeper
will sound as a warning. Stop cleaning the sensor.
If a smudge that cannot be removed with a blower remains, having the
sensor cleaned by a Canon Service Center is recommended.
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