Canon AE-1 - Manual (Page 58)

Adapter A for T ripod
When using a lens of considerable overall
length, depending on the tripod being used, it
may be difficult to hold the adjustment in the
case of accidental bumping of the lens.
In such cases, the Canon Adapter A for
Tripod with a rubber matte should be placed
between the tripod and the camera for easier
handling.
Composition
Since the AE-1 has automatic exposure
control with shutter priority, you can con­
centrate on the actual picture you are going to
take without worrying about exposure differ­
ences that may occur with changing subjects.
Viewing is performed through the lens, and
there is no difference between the viewfinder
image and the image exposed on the film, as
opposed to the image provided by a separate
viewfinder which is affected by the parallax
between the viewfinder and the camera lens.