Flash Photography; Using The Built-In Flash; Auto Pop-Up Modes - Nikon D750 User Manual

Flash Photography

Using the Built-in Flash

The built-in flash can be used not only when natural lighting is
inadequate but to fill in shadows and backlit subjects or to add a
catch light to the subject's eyes.

Auto Pop-up Modes

In i, k, p, n, o, s, w, and g modes, the built-in flash
automatically pops up and fires as required.
1
Choose a flash mode.
Keeping the M (Y) button pressed, rotate the main
command dial until the desired flash mode appears in the
information display.
M (Y) button
180
Main command
dial
Information display