Canon EOS 5D Mark III Instruction Manual page 66

A Fully Automatic Shooting (Scene Intelligent Auto)
The shutter speed display is blinking.
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Since it is too dark, taking the picture may result in a blurred subject due
to camera shake. Using a tripod or a Canon EX-series Speedlite (p.188)
(sold separately) is recommended.
When flash was used, the bottom part of the picture came out
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unnaturally dark.
If a hood is attached to the lens, it can obstruct the flash coverage. If the
subject is close, detach the hood before taking the picture with flash.
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