Grass Valley LGK-3901 - Manual (Page 36)

GUIDE TO INSTALLATION AND OPERATION
30 | LGK-3901/DSK-3901
Figure 4.4 Linear Keying
Full keying is where the Fill signal needs to be multiplied by the Key signal prior to being added to the modified
Background signal. In this case, the Fill has not already been cut by its key external to the LGK-3901/DSK-3901. The
card cuts a hole in the Fill with the Key and then cuts a hole in the Background with a computed (1 - Key) signal. The
cut Fill and cut Background are then added together.
Figure 4.5 Full Keying
Key invert replaces the Key output with (1 - Key), thereby inverting the action of the Key.
4.8.5.4 Sense
The LGK-3901/DSK-3901 supports Normal and Invert Sense.
• Normal
o Black-level key signal causes Fill image to be fully transparent so it will not appear over a background
o White-level key signal causes Fill image to be opaque with no background appearing through it
o Intermediate keying levels produce a pro-rata transparency effect
• Invert
o Reverses the effect seen with Normal Sense
o White-level key signal causes Fill image to be fully transparent so it will not appear over a background
o Black-level key signal causes Fill image to be opaque with no background appearing through it
o Intermediate keying levels produce a pro-rata transparency effect