Canon EF - Manual (Page 68)

Taking Pictures by Flash
Even though the Canon EF can take pictures by
candlelight, there are certain situations which require
using an external light source. In dim light, when
you want to stop fast action or take crystal clear
snapshots full of vivid colors and fine details, you
need flash. If you want to avoid harsh shadows when
shooting in bright sunlight, flash can be used as fill-in
light. At night, a nearby subject can be illuminated
with flash. Since the Canon EF uses a vertically
moving metal focal plane shutter, synchronization
with electronic flash is possible at all speeds up to
and including 1/125 sec. With a flash hot shoe built
into the top of the pentaprism, the EF can easily
accept any direct mounting electronic flash unit,
including the specially-designed Canon Speedlite
133D. This flash unit (with the Flash-Auto Ring A
2
or B
2
attached to the front bayonet of the lens)
employs the Canon Auto Tuning (CAT) System to
determine the proper exposure in flash photography.
The focused distance of the lens and the charging
level of the 133D are sent as electrical signals to the
camera's Variable Aperture AE control, which then
adjusts the diaphragm automatically to produce
,Left: Canon FD 35mm f/2 S.S.C., B at f/16, ASA 400.
Right: Canon FD 100—200mm f/5.6 S.C., Double Exposure,