Canon AE-1 - Manual (Page 44)

^ Setting the Shutter Speed
* The shutter dial controls the length of
time that light is allowed to reach the film. On
the shutter speed dial, shutter speeds from
1/1000 to "B" are marked in white, while the
2-second speed is marked in orange. Each
shutter speed gradation is twice or ap­
proximately twice the preceding speed,
beginning with 1/1000 sec. (1000).
Thus, the light reaching the film at 1/250
second is half the light reaching it at 1/125.
The numbers on the shutter speed scale
represent the corresponding fraction of a
second (125= 1/125), with the exception of 1
and 2 (marked in orange) which stand for 1
and 2 seconds respectively.
The “B" setting is for long exposures. At
the "B" setting, the shutter remains open
while the shutter button is depressed and
closes when it is not depressed. See page 48
for more details concerning long exposures.
To set the shutter speed, rotate the dial in
either direction until the desired number
clicks into place next to the white index
mark. An in-between setting should not be
used, and the shutter speed dial cannot be