Nikon D780 Reference Manual page 207

A
Getting Good Results with Autofocus
The camera may be unable to focus under the conditions listed below, in
which case the shutter release may be disabled or pictures may be out of
focus, the latter a result of the camera either displaying the in-focus
indicator ( I )—or, in live view, displaying the focus point in green—when
the subject is not in focus. Focus manually or use focus lock to focus on
another subject at the same distance.
•
There is little contrast between the subject and the background, as may
be the case if the subject is photographed against a featureless wall or
the background is the same color as the subject.
•
The focus point contains objects at different distances from the camera,
as may be the case if the subject is inside a cage.
•
The subject is dominated by regular geometric patterns such as the
rows of windows in a skyscraper.
•
The focus point contains areas of sharply contrasting brightness, as may
be the case if the subject is half in the shade.
•
Background objects appear larger than the main subject, as may be the
case if a building is in the frame behind the subject.
•
The subject contains many fine details, as may be the case when the
subject is a field of flowers.
Shooting Settings
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