SIGMA DP3 Quattro - Manual (Page 48)

48
LCD DISPLAY IN M MODE
When the exposure is set as M mode, the LCD Display reflects the
selected exposure on the screen so that photographers can confirm how
the actual image will look. When the exposure is under, it becomes darker,
and when it is over, it becomes brighter.
When you shoot images in M mode while using the flashguns from other
companies, the display would be dark, and make it difficult to check the
details of the image, such as the focus point and composition. In this case,
it is recommended to change the setting to [Off], and adjust the brightness
of the image on screen.
Select from [ Capture Settings] (P.27) → [Preview Exposure in M
Mode].
Off Brightness of the LCD Display is automatically
adjusted for better visibility.
On (Default) The selected exposure value is reflected in the LCD
Display.
TIP

When ELECTRONIC FLASH EF-140S SA-STTL is used with the
camera, the brightness of the LCD Display is automatically adjusted for
better visibility even when the function is [ On].