Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 60)

Attaching and Detaching a Lens
60
While pressing the lens release
button, turn the lens as shown by
the arrow.
Turn the lens until it stops, then
detach it.
Attach the rear lens cap to the
detached lens.
Detaching the Lens
Do not look at the sun directly through any lens. Doing so may cause
loss of vision.
When attaching or detaching a lens, set the camera’s power switch to
<
2 >.
If the front part (focusing ring) of the lens rotates during autofocusing, do
not touch the rotating part.
Minimizing Dust
When changing lenses, do it quickly in a place 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.