Grass Valley Kayenne XL Package v.7.0.4 - Manual (Page 47)

Kayenne XL Package — User Manual 45
Keying
Figure 10. Key Hi, Clip Lo vs. Clip and Gain
In this mode, Gain changes when either control is adjusted. The difference
between the upper and lower keying thresholds is equivalent to gain:
• Clip Hi = Clip + Gain/2
• Clip Lo = Clip – Gain/2
Clip Hi and Lo control is more appropriate for low gain keys, to enable
independent control of the two thresholds. For example, when adjusting a
linear key the operator wants to control where the fill becomes opaque
(Clip Hi) and where the fill becomes transparent (Clip Low). In Clip Hi/Lo
mode adjusting the point of opacity does not change the point of transpar-
ency, and vice versa.
Clip, Gain, Clip Hi and Clip Low adjustments always interact. Changing
one always results in changes to two other values. Changing Clip Hi or Clip
Low changes both Clip and Gain, not just Gain.
S-Shaped Key Signals
On the Kayak HD system, an S-shaping function is applied to the edges of
luminance keys. S-shaping smooths the sharp corners of a luminance key
control signal, which helps prevent banding artifacts. S-shaping a signal
minimally affects the key edges, and does not move key thresholds or affect
the overall gain of the key.
Figure 11. S-Shaped Luminance Key Control Signal
Key Cut
Signal
Clip
Gain
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Clip Hi
Clip Lo
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Key Control Signal S-Shaped
Key Control Signal