Nikon D5100 Reference Manual page 24

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Hiding Shooting Information
To turn the monitor off, press the R button. Note that the monitor turns off automatically
while the shutter-release button is pressed or if no operations are performed for about 8 s
(for information on choosing how long the monitor stays on, see Custom Setting c2 (Auto
off timers, 0 160)). The information display can be restored by pressing the R button
again.
X
R button
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Rotating the Camera
When the camera is rotated 90 °, shooting information rotates to
match camera orientation.
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The Shutter-Speed and Aperture Displays
These displays provide visual indications of shutter speed and aperture.
Fast shutter speed, large aperture
While the mode dial is rotated, this display is replaced by an image of the mode dial.
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See Also
For information on choosing a design for the information display, see Info display format,
(0 168). For information on choosing whether information is displayed automatically; see
Auto info display (0 170). For information on the indicators displayed in live view, see page
103.
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Information display
(small f-number).
Slow shutter speed, small aperture
(large f-number).
Monitor off