Nikon 1 J3 Reference Manual page 80

A
The Movie Crop
The movie crop is shown in the monitor.
A
Focus Lock
If Single AF is selected for Focus mode in the movie menu for
advanced movie mode, focus will lock while the shutter-release button
is pressed halfway (0 135).
y
60
HD crop (16 : 9) Slow-motion movie crop
(8 : 3)