Keying with Keylight

This section explains how to use the blue/green screen keyer, Keylight, in Nuke.

Quick Key

Consider this shot from The Saint, pictures courtesy of CFC and Paramount British Pictures Ltd.

Blue screen.

The figure above is the blue screen foreground that should be composited over the background shown below.

1.   Start Nuke and read in both images. From the Keyer menu, apply Keylight and attach a Viewer.
2.   Click the color swatch next to ScreenColor to activate the eye dropper. In the Viewer, Ctrl/Cmd+Shift+Alt+click and drag a rectangular area over the blue pixels as shown below.

Picking the screen color also sets the ScreenBalance.

That’s it. In many cases, this is all you need to do to perform a key, since selecting the screen color creates a screen matte and despills the foreground.

3.   Switch output from FinalResult to Composite to see the foreground keyed over the background. The final composite is shown below.

Picking the screen color may be enough for a lot of keys, but there are many more tools within Nuke that can be used to tackle more complicated shots. These are described later in this chapter.