Canon EOS-1D C Instruction Manual page 380

Troubleshooting Guide
The maximum burst during continuous shooting is lower.
If you shoot something that has fine detail (such as a field of grass),
the file size will be larger and the actual maximum burst may be lower
than the number mentioned on page 124.
ISO 100 cannot be set/ISO speed expansion cannot be
selected.
If [z2: Highlight tone priority] is set to [Enable], the settable ISO
speed range will be ISO 200 - 51200 (ISO 200 - 25600 for movie shooting).
Even if you expand the settable ISO speed range in [ISO speed range],
you cannot set expanded ISO speeds (L, H, H1, or H2). If [z2: Highlight
tone priority] is set to [Disable], ISO 100/125/160 can be set (p.154).
The Auto Lighting Optimizer cannot be set.
If [z2: Highlight tone priority] is set to [Enable], the Auto Lighting
Optimizer cannot be set. If [z2: Highlight tone priority] is set to
[Disable], then the Auto Lighting Optimizer can be set (p.154).
Even though I set a decreased exposure compensation, the
image comes out bright.
Set [z2: Auto Lighting Optimizer] to [Disable]. When [Standard/
Low/High] is set, even if you set a decreased exposure compensation or
flash exposure compensation, the image may come out bright (p.150).
The Live View image or captured image is not displayed
during multiple-exposure shooting.
If [On:ContShtng] is set, Live View display, image review after image
capture, and image playback are not possible during shooting (p.184).
The multiple-exposure image is shot in 1 quality.
When the image size is set to 41 or 61, the multiple-exposure
image will be recorded in 1 quality (p.190).
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