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Keying with ChromaKeyer

This section explains how to use the blue/green screen keyer, ChromaKeyer, in Nuke. ChromaKeyer can take advantage of modern GPUs and multi-core CPUs to accelerate the keying process when used for compositing in Nuke's Node Graph. ChromaKeyer is also available as a soft effect in Nuke Studio's timeline environment.

Quick Key

The images below show a green screen foreground and the background to be composited over.

Foreground Background
1.   Start Nuke and read in the foreground and background images. From the Keyer menu, select ChromaKeyer and attach a Viewer.
2.   In the ChromaKeyer Properties panel, click the color swatch next to screen color to activate the eye dropper.
3.   Ctrl/Cmd+Shift+click and drag a rectangular area over the green pixels in the Viewer. This averages the pixels in the area selected to produce a better key.

In some 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.

4.   Merge the foreground over the background to produce your final comp.

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. See Improving Mattes, Despilling and Color Replacement, and Multi-Pass Keying for more information.