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How should I set Clip/Gain Options?
Adjustable Linear keys: Use Clip Hi / Clip Lo
Luma keys: Use Clip / Gain
Chroma keys: Use Clip Hi / Clip Lo
Traditionally, Luminance Keys have used Clip/Gain adjustments, setting the brightness on which to key (Clip) and adjusting the extent of softness (Gain).
But for Adjustable Linear Keys and Chromakeys, it makes more sense to use Clip Hi/Clip Lo adjustments. If you imagine the key signal of a key, Clip Lo and Clip Hi determine the points at which the key becomes opaque and/or transparent.
If your CG's key signal is putting out grey instead of black when there's no text, Adjustable Linear mode allows Clip Lo to adjust the point at which the CG becomes invisible - without affecting the point at which white text would become opaque. Similarly, if the video level of the CG key is arriving at your Kalypso too low, you can adjust Clip Lo to make the white areas opaque without affecting the point at which "nothing" becomes invisible. Likewise, Chromakey adjustments are easier when you are adjusting only one end of the keying equation, either the see-through-ness of the talent, or the noise on the background.
Level differences on CG key signals are less likely in a purely digital world, but occasionally we have signals that come from analogue gear through A to D converters and levels can go awry.
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