When autofocus fails, Subjects difficult to focus, Set the lens focus mode switch to <mf – Canon EOS-1D Mark IV User Manual
Page 100: Focus the subject
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When Autofocus Fails
Autofocus can fail to achieve focus (the focus confirmation light <•>
blinks) with certain subjects such as the following:
Subjects difficult to focus
• Very low-contrast subjects
(Example: Blue sky, solid-color walls, etc.)
• Subjects in very low light
• Extremely backlit or reflective subjects
(Example: Car with a highly reflective body, etc.)
• Near and far subjects covered by an AF point
(Example: Animal in a cage, etc.)
• Repetitive patterns
(Example: Skyscraper windows, computer keyboards, etc.)
In such cases, do one of the following:
(1) With One-Shot AF (p.95), focus an object at the same distance
as the subject and lock the focus before recomposing.
(2) Set the lens focus mode switch to <MF> and focus manually.
MF: Manual Focusing
Set the lens focus mode switch to
<MF>.
Focus the subject.
• Focus by turning the lens focusing
ring until the subject looks sharp in
the viewfinder.
Q During automatic AF point selection (p.97), if you hold down the shutter
button halfway and focus manually, the focus confirmation light <•> will
light when the center AF point achieves focus.
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