Nikon D5200 Reference Manual page 122

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HDMI and Other Video Devices
When the camera is connected to a video device, the device will
display the view through the camera lens. If the device
supports HDMI-CEC, select Off for the HDMI > Device control
option in the setup menu (0 147) before shooting in live view.
If 1920 × 1080 60i, 1920 × 1080 50i, 1280 × 720 60p, or 1280
× 720 50p is selected for Frame size/frame rate, the monitor
will turn off when the camera is connected to an HDMI video device.
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See Also
For information on the indicators displayed in live view, see page 97. For information on
choosing focus and AF-area modes, see page 94. See page 100 for information on focusing
in live view.
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