Nikon D780 Reference Manual page 326

D
[RAW Slot 1 - JPEG Slot 2]
•
If [On] is selected for [Multiple exposure] > [Save individual images
(NEF)] in the photo shooting menu, or if [On] is selected for [HDR (high
dynamic range)] > [Save individual images (NEF)] in the photo
shooting menu, unprocessed copies of the individual NEF (RAW) photos
that make up each multiple exposure or HDR image will be recorded to
both memory cards together with the JPEG composite, regardless of the
option selected for image quality.
•
If [On] is selected for Custom Setting d8 [Save original (EFFECTS)],
unprocessed NEF (RAW) copies of pictures taken in f , d , e , k , l , and
m modes will be saved to both memory cards together with the final
JPEG picture, regardless of the option selected for image quality.
A
[Backup] and [RAW Slot 1 - JPEG Slot 2]
•
The control panel and viewfinder show the number of exposures
remaining on the card with the least amount of space available.
•
Shutter release will be disabled when either card is full.
A
Recording Movies
When two memory cards are inserted in the camera, the slot used to
record movies can be selected using the [Destination] item in the movie
shooting menu.
280 Other Shooting Options