Canon REBEL SL1 EOS 100D Instruction Manual page 19

Setting the Flash*
You can set the flash sync speed for
flash photography in the aperture-priority
AE (AM) mode.
AUTO: Auto
The flash sync speed is set automatically within a range of 1/200
sec. to 30 sec. to suit the scene's brightness. High-speed sync is
also possible.
!_6%°A: 1/200 -1/60 sec, auto
Prevents a slow shutter speed from being set in low-light conditions.
It is effective for preventing subject blur and camera shake.
However, while the subject will be properly exposed with the flash,
the background may come out dark.
1/200:1/200 sec, (fixed)
The flash sync speed is fixed at 1/200 sec. This more effectively
prevents subject blur and camera shake than with [1/200-1/60 sec,
auto]. However, in low light, the subject's background will come out
darker than with [1/200-1/60 sec, auto].
_L_ If [4/200-I/60 sec. auto] or [11200sec. (fixed)] is set, high-speed sync is
not possible in the <Av > mode.
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