Canon A-1 - Manual (Page 28)

Setting the ASA Film Speed
The ASA is a numerical rating of a film's
sensitivity to light. The higher the ASA
rating, the faster the film and the more
sensitive it is to a given amount of light as
compared to a film of a lower ASA rating. In
other words, the higher the ASA rating, the
less light you need to expose the film. When
buying film, choose one with an ASA rating
appropriate for the lighting conditions. The
film manufacturer's recommended ASA
rating can be found on the film packaging or
data sheet.
Since the ASA film speed is one of the
essential factors in determining proper ex-
posure, it is very important that it be
correctly set on the camera. The table on the
opposite page shows the ASA ratings which
can be set on the A-1. Figures in parentheses
are intermediate film speeds which are in-
dicated by dots on the ASA dial. To set the
ASA, press in the ASA film speed dial lock
button with your fingernail and turn the
outer knurled edge of the dial until the
desired film speed rating is aligned with
the film speed index. The dial cannot be
turned lower than ASA 6 or higher than
ASA 12800.
There is an exposure compensation scale on
the ASA film speed setting dial. The func-
tion of this scale will be explained later, but
at this point, please note that this scale
should be set at “ 1 ” for normal AE pho-
tography.
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