Nikon D5100 Reference Manual page 12

Follow the steps below to record a series of two or three exposures in a single
photograph. Multiple exposures can make use of RAW data from the camera image
sensor to produce colors noticeably superior to those in software-generated
photographic overlays.
II Creating a Multiple Exposure
Multiple exposures can not be recorded in live view. Exit live view before proceeding.
Note that at default settings, shooting will end and a multiple exposure will be
recorded automatically if no operations are performed for about 30 s.
[] Extended Recording Times
For an interval between exposures of more than 30 s, select On for the Image review
(_ 150) option in the playback menu and extend the monitor-off delay for image review
using Custom Setting c2 (Auto off timers, _ 160). The maximum interval between
exposures is about 30 s longer than the option selected for Custom Setting c2. If no
operations are performed for approximately 30 s after the monitor has turned off during
playback or menu operations, shooting will end and a multiple exposure will be created
from the exposures that have been recorded to that point.
2
Select Multiple exposure.
Press the MENU button to display the menus.
Highlight Multiple exposure in the
shooting menu and press I_.
MENU b utton
Enable multiple exposure mode.
Highlight Multiple exposure mode and
press I1_.
The options shown at right will be displayed.
Highlight On and press _).
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