Nikon D3100 Reference Manual page 98

A
The E Button
Exposure compensation can also be
set by pressing the E button and
rotating the command dial. The
selected value is shown in the
viewfinder and information display.
A
Mode M
In mode M, exposure compensation affects only the exposure indicator; shutter speed and
aperture do not change.
A
Using a Flash
When a flash is used, exposure compensation affects both background exposure and flash
level.
t
82
E button
Command dial
–0.3 EV +2 EV