Canon EOS Rebel SL1 18-55mm IS STM Lens Kit - Manual (Page 171)

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Using AF to Focus (AF Method)
If focus is not achieved with the shooting conditions on the preceding
page, set the lens focus mode switch to <MF> and focus manually.
If you use AF with any of the following lenses, using [Quick mode] is
recommended. Autofocusing with [u+Tracking], [FlexiZone - Multi] or
[FlexiZone - Single] may take longer or correct focus may not be
achieved.
EF50mm f/1.4 USM, EF50mm f/1.8 II, EF50mm f/2.5 Compact Macro,
EF75-300mm f/4-5.6 III, EF75-300mm f/4-5.6 III USM
For information on discontinued lenses, refer to your local Canon Web site.
If you shoot a peripheral subject and it is slightly out of focus, aim the
center AF point or zone over the subject to focus, focus again and then
take the picture.
The AF-assist beam will not be emitted. However, if an EX-series
Speedlite (sold separately) equipped with an LED light is used, the LED
light will turn on for AF-assist when necessary.
In magnified view, the higher the magnification, the more difficult
focusing will be because of camera shake during handheld shooting (as
well as when the lens focus mode switch is set to <MF>). Using a tripod
is recommended.
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