SIGMA DP3 Quattro - Manual (Page 90)

90
FLASH EXPOSURE COMPENSATION
It is possible to compensate the flash output level without changing the
background’s exposure.
The Flash Exposure Compensation can be set from [ Capture Settings]
(P.27) → [ Flash] → [Flash Exposure Compensation].
Select the desired compensation value by using the buttons.

Flash Exposure compensation can be set in 1/3 stop increments from
+3.0 to -3.0 stops.

When the Flash Exposure Compensation is set, the icon
and compensation value will be displayed on the left of
the LCD monitor.
CAUTION!!

The flash exposure compensation can not be set if the flashgun is not
attached to the camera, or the flashgun is turned off.

The flash exposure compensation will not disable automatically. After
taking the picture, set the compensation value to ±0.0 by above
procedure.