Nikon D3200 Reference Manual page 59

Image overlay combines two existing NEF (RAW) photographs to create a single
picture that is saved separately from the originals; the results, which make use of RAW
data from the camera image sensor, are noticeably better than overlays created in an
imaging application. The new picture is saved at current image quality and size
settings; before creating an overlay, set image quality and size (_ 44, 46; all options
are available). To create an NEF (RAW) copy, choose an image quality of NEF {RAW).
4-
Select Image overlay.
Highlight Image overlay in the retouch menu
and press I_.
The dialog shown at right will be displayed, with
Image 1 highlighted; press _) to display a list of
the NEF (RAW) pictures created with this camera.
2
Select the first image.
Use the multi selector to highlight the first
photograph in the overlay. To view the
highlighted photograph full frame, press and
hold the e button. Press _) to select the
highlighted photograph and return to the
preview display.
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