Canon POWERSHOT S100 User Manual page 104

You can lock the exposure and shoot, or set the focus and exposure
separately to shoot. AE stands for "Auto Exposure".
Lock the exposure.
Point the camera toward the subject and
press the A button while pressing the
shutter button halfway.
When _ appears, the exposure will be
locked.
ff you re_ease your finger from the shutter
button and press the A button again, =,X =
will disappear and AE will unlock.
Compose the scene and shoot.
When you shoot one image, =X" will
disappear and AE will unlock.
If you lock the exposure and turn the _ dial, you can change the shutter speed
and aperture value combination.
Just as with the AE lock (see above), you can lock the exposure for shooting
with the flash. FE stands for "Flash Exposure".
Choose _ (p. 81).
Lock the flash exposure.
Point the camera toward the subject and
press the ,_ button while pressing the
shutter button halfway.
The flash will fire and when -_ appears,
the flash output will be retained.
If you release your finger from the shutter
button and press the ,_ button again,
will disappear and FE will unlock.
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