Grass Valley DD35 Family v.3.1.5 - Manual (Page 107)

2. Panel Operation DD35 Production Switcher
2 – 73 Operating Instructions – Rev. 16 / 10.2001
Forc FGND The Forc FGND button serves to select whether the mask should suppress (mask)
or force the foreground picture. If the button lights up, Forced Foreground is active.
Mask inv The Mask inv button can be used to invert the mask signal.
This means that, for instance, with a square mask, not the inside but the outside
of the square is used for masking.
Mask PVW The Mask PVW button is used to highlight the mask signal on the preview monitor.
This function serves to adjust the mask.
Note: In Mask PVW mode, the mask is only represented as a 1-bit signal.
If you want to exactly position a mask with softness, simply switch on
the mask with the Mask on key in the Keyers panel.