Nikon D5100 Reference Manual page 51

All colors other than the selected colors
are recorded in blackand white. The effect
can be chosen during live view (_ 120).
The built-in flash turns off; use of a tripod
is recommended when lighting is poor.
At
Silhouette subjects against bright
backgrounds. The built-in flash turns off;
use of a tripod is recommended when
lighting is poor.
Use with bright scenes to create bright
images that seem filled with light. The
built-in flash turns off.
Use with dark scenes to create dark,
somber images with prominent
highlights. The built-in flash turns off; use
of a tripod is recommended when lighting
is poor.
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