Nikon D3400 Reference Manual - English - Page 141

Flash Compensation Flash compensation is used to alter flash output from the level suggested by the camera, changing the brightness of the main subject relative to the background. Flash output can be increased to make the main subject appear brighter, or reduced to prevent unwanted highlights or reflections (0 299). Keep the M (Y) and E (N) buttons pressed and rotate the command dial until the desired value is selected in the viewfinder or information display. In general, positive values make the main subject seem brighter while negative values make it seem darker. Normal flash output can be restored by setting flash compensation to ±0. Flash compensation is not reset when the camera is turned off (in scene mode, flash compensation will be reset when another mode is selected or the camera is turned off). M (Y) button + Command dial Information display E (N) button -0.3 EV +1 EV P, S, A, and M Modes 117