Canon Speedlite 600EX-RT Mode D'emploi page 110

Troubleshooting Guide
The bottom of the picture looks dark.
You were too close to the subject. Move away from the subject.
When shooting within 1 m (3.3 ft.) of the subject, set the bounce
position down by 7°.
Remove the lens hood if attached.
The picture periphery looks dark.
Set the flash coverage to the automatic setting (p.29).
When using the manual setting for the flash coverage, set a flash
coverage that is wider than the shooting angle of view (p.30).
Check that C.Fn-21-1 is not set (p.100).
The picture is very blurred.
When the shooting mode is set to <W> and the scene is dark, slow
sync is enabled automatically (the shutter speed becomes slower). Use
a tripod, or set the shooting mode to <V> or fully automatic mode
(p.19). Note that you can also set the sync speed in [Flash sync.
speed in Av mode] (p.44).
The flash coverage is not set automatically.
Insert the mounting foot into the camera's hot shoe all the way, slide the
lock lever to the right, and secure the Speedlite to the camera (p.15).
Set the flash coverage to <L> (Automatic) (p.29).
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