Canon AE-1 - Manual (Page 44)

in 9 « the shutter speed until the meter
needle indicates f/22 and then decrease the
shutter speed by one gradation so that the ex«
posure will be correct.
Underexposure and
Coupling Range Warning LED Lamp
This lamp blinks on arxi off as a warning
of incorrect exposure. If you reduce the
shutter speed by turning the shutter speed dial
so the underexposure warning lamp will stop
blinking, the correct exposure will be
obtained.
Under dim light with a slow speed lens»
there is a case when the meter needle will
point at the aperture scale inside the view*
finder although it will exceed the maximum
aperture of the lens. In this case» turn the
shutter speed dial to a slower setting so that
the underexposure warning lamp stops blink*
ing.
For example, when you use an f/2.8 lens
pid the meter needle exceeds the aperture
scale of f/2.8 inside the viewfinder, reduce the
shutter speed until the lamp stops flashirsg.
When the shutter speed is set at ''B"*
(Bulbl and the shutter button is pressed
halfway» this warning lamp will also flash on
and off.