Canon A-1 Repair Manual page 6

(3) Light Sensing Element
Center-weighted average meter reading (the same as the
AE-l) by a silicon photocell placed above the eyepiece
and fresnel lens to concentrate the incoming light.
(4) Meter Coupling Range
EV -2 (f/l.4 lens) to EV 18 with ASA 100 film. The
programmed AE program is shown by the dotted line.
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