Canon AV 1 - Manual (Page 23)

Dismounting
1. Turn the Breech-lock ring counterclock­
wise until it stops.
2. Pull the lens out from the camera body.
When removing a lens, take special care not
to damage the protruding pins and levers on
the rear. With the exception of the Fish-eye
7.5mm lens, always put a lens down with
the rear facing up.
For more information on general use and
care of the lens, please see the lens instruc­
tion booklet.
Note
Since the following two FL lenses might cause
damage to the camera, they cannot be mounted
on the AV-1:
FL19mm f/3.5, FL58mm f/1.2.
The following two F L lenses may be mounted,
but, for technical reasons the camera's built-in
meter becomes unreliable and is unusable:
FL35mm f/2.5, FL50mm f/1.8.
One of these lenses may be mounted only
after the film has been completely advanced.