Canon EOS 5D Mark III Instruction Manual (en)

Troubleshooting Guide
If [z3: Highlight tone priority] is set to [Enable], the Auto Lighting 
Optimizer cannot be set. When [z3: Highlight tone priority] is set to 
[Disable], then the Auto Lighting Optimizer can be set (p.148).
Set [z2: Auto Lighting Optimizer] to [Disable]. When [Standard/
] is set, even if you set a decreased exposure compensation or 
flash exposure compensation, the image may come out bright (p.171).
If [On:ContShtng] is set, Live View display, image review after image 
capture, and image playback are not possible during shooting (p.179).
When the image-recording quality is set to 41 or 61, the 
multiple-exposure image will be recorded in 1 quality (p.185).
If you shoot at night when the background is dark, the shutter speed 
becomes slow automatically (slow-sync shooting) so that both the subject 
and background are properly exposed. To prevent a slow shutter speed, 
under [z1: External Speedlite control], set [Flash sync. speed in 
Av mode
] to [1/200-1/60 sec. auto] or [1/200 sec. (fixed)] (p.194).
Make sure the flash (or PC sync cord) is securely attached to the camera.
If you use a non-Canon flash unit with Live View shooting, set [z4: 
Silent LV shoot.
] to [Disable] (p.208).
The Auto Lighting Optimizer cannot be set.
Even though I set a decreased exposure compensation, the 
image comes out bright.
The Live View image or movie shooting image is not 
displayed during multiple-exposure shooting.
The multiple-exposure image is shot in 1 quality.
When I use the <f> mode with flash, the shutter speed 
becomes slow.
The flash does not fire.