Canon AT 1 - Manual (Page 66)

Holding the Camera
The electromagnetic shutter release
button has a short, soft touch. The shutter
can be released by lightly depressing the
.shutter button to help prevent camera shake.
But, unsteady holding of the camera will
cause camera shake in spite of the electro­
magnetic shutter release system.
Therefore, be sure to hold the camera
firmly. Rest the camera on your left palm and
grasp the lower part of the lens focusing ring
between your thumb and forefinger or middle
finger. Hold the right end of the camera
firmly, with your right thumb behind the tip
of the film advance lever and your right fore­
finger on the shutter button, while the other
fingers hold the camera's finger grip.
To reduce camera shake, press your left
elbow strongly against your body and look
into the viewfinder steadying the camera
against the forehead. The right arm should be
relaxed while holding the camera.