Canon AE-1 - Manual (Page 88)

Stopped-Down Metering
When the AE-1 is used with Canon FD
lenses, photography can be performed with
through-the-lens (TTL) metering and with AE
coupling. However, with the Canon FL lenses
and most accessories such as bellows, ex­
tension tubes, or a microscope adapter, it is
necessary to take a stopped-down meter
reading.
Stopping down the lens can be done by
pushing the stopped-down lever until it locks.
When the lens is stopped-down, press the
shutter button halfway or depress the ex­
posure preview switch and adjust the aper­
ture ring and/or shutter speed dial until the
meter needle inside the viewfinder is aligned
with the stopped-down metering index mark.
Press the shutter button and the photo­
graph will be perfectly exposed. If the lens
should be mounted on the camera with the
stopped-down lever locked, correct exposure
will not be obtained. In this case, a red
warning mark by the stopped-down coupling
lever inside the camera body is visible. After
removing the lens, on the lower part of the
camera body, just below the mirror, this