Canon EOS-1DS Mark III Instruction Manual page 131

Sensor Cleaning
The camera has a Self Cteaning Sensor Unit attached
to the sensor's front layer (low-pass fitter) to shake off
dust automatically.
The Dust Delete Data can also be appended to the
image so that any remaining dust spots can be removed
automatically by the Digitat Photo Professional
(provided software).
Minimizing Dust
® When changing lenses, do it in a pJace with minimal dust.
® When storing the camera without a lens attached, be sure to
attach the body cap to the camera.
® Remove dust on the body cap before attaching it.
Even while the Self Cleaning Sensor Unit is operating, you can
press the shutter button hal_ay t° inte[ru#t the c!eaning and start
shooting immediately,