User guide

KeylightThe Foundry

ADVANCED KEYING

Grow & Shrink

This control should not normally be used as eroding the edges can produce

a very poor key. However, this parameter allows you to grow (if greater

than zero) or shrink (if less than zero) the alpha in the Screen Matte. These

controls are sub-pixel accurate.

Despot

This controls how much to simplify the matte. It coagulates similar regions

so that, for example, black specks in the white matte can be absorbed by

the surrounding white areas. Decreasing the Despot will remove isolated

spots of black in the white matte. Increasing Despot will remove isolated

spots of white in the background up to that size.

Colour

Replacement

Remember that Keylight does two things - it removes the screen colour to

despill the image and generates an alpha (Screen Matte) to composite the

foreground over the background layer.

If you then process the Screen Matte, for example, by eroding the matte or

changing the clip levels, Keylight will be removing the wrong amount of

screen colour from the pixels whose transparency have now changed. The

Replace Method instructs Keylight how to deal with such pixels. The Status

Figure 48. Screen Matte. Figure 49. Eroded Matte.

Figure 50. Eroded matte. Figure 51. Despot.