Canon A-1 - Manual (Page 27)

Lens Hood
When shooting into bright light, light rays
entering the lens may form defects on the
image called ghost and flare. Attaching a
hood onto the lens helps to prevent this.
Bayonet-mount hoods are available as op­
tioned accessories for most Canon lenses.
Please use only that hood which is specified
for the lens concerned. This type of hood
fits into the bayonet mount at the front of
the lens where it is fixed by turning until it
is tight. Some hoods for wide-angle lenses
require proper positioning before mounting.
Align the red dot on this type of hood with
the notch in the bayonet mount at the front
of the lens. Then lightly push the hood into
the mount tmd turn it until it is tight.
When not in use, the hood can be mounted
in reverse on a standard or some wide-angle
lenses, in which case even the hood will fit
perfectly into the camera’s case.
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