Quick links to procedures on this page:
You can specify how overlay clips blend with the background by using different "Key" options:
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Chroma Key — used to remove a specific color from an overlay clip. For example, if you capture a subject against a "green screen" background or cover part of a subject with green, Chroma Key can be used to remove the green. You can then place the subject on another background to change the surroundings or create a special effect such as the appearance of a hovering object. |
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Gray Key — adjusts the transparency of the overlay clip based on tone (light/dark values), rather than color. |
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Multiply — multiplies the value of the overlay colors with the underlying colors and divides by 255. The result is darker than the original colors. White has no blend effect; black always blends to black. You can use the Blend/Opacity slider to adjust the transparency. |
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Add Key — adds the color values of the overlay clip with the values of the underlying colors. You can use the Blend/Opacity slider to adjust the transparency. |
The settings available depend on the type of key that you choose. Experiment with the settings to achieve the look you want.
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Click Mask & Chroma Key in the Attribute tab. |
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Enable the Apply Overlay Options check box, then choose one of the following settings from the Type drop-list: |
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If you choose Chroma Key, use the eye dropper tool  to pick a color in the Preview Window and adjust the color similarity value (to the right of the eye dropper tool). The transparency effect appears in the Preview Window. |
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Gamma — affects image contrast and can be used to lighten (move control to the right) or darken (move control to the left) the overall image |
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Min — can be moved to the right to darken the image’s lightest pixels |
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Max — can be moved to the left to lighten the image’s darkest pixels |
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Cutoff — can be moved to the right to set a new black point for the image (more black in the image). |
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Threshold — can be moved to the left to set a new white point for the image (more white in the image). |
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If you choose Multiply or Add Key, you can also adjust the Blend/Opacity setting to adjust transparency. |
You can crop an overlay clip by adjusting the Width and Height values.
You can invert the blend settings by enabling the Invert check box.
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