Canon AE-1 - Manual (Page 92)

lens is mounted on the camera, the diaphragm
blades will open or close by turning the
aperture ring. To revert from manual aperture
control, reset the manual lock lever at the
position of the white dot.
3 Lock for Manual Aperture Control
When Using the Macrophoto Coupler (3)
In close-up photography of high mag­
nification with a lens reversed on the Macro-
photo Coupler, the automatic diaphragm
mechanism is not coupled. You must, there­
fore, remember to close down the diaphragm
manually after having locked the automatic
aperture lever in the manual position as ex­
plained above in (1) and (2). Then, fix the
Macrophoto Hood on the lens mount by
turning the bayonet ring.
When you are taking stopped-down meter
readings, the manual aperture control "M"
signal above the aperture scale inside the
viewfinder flashes on and off only when the
shutter release button is depressed halfway.