Apple MA434Z/A User Manual - Page 706

Keylight Keylight is an Academy Award-winning keyer from Framestore CFC based in England. It accurately models the interaction of the bluescreen or greenscreen light with the foreground elements, and replaces it with light from the new background. With this approach, blue spill and green spill removal becomes an intrinsic part of the process, and provides a much more natural look with less tedious trial-and-error work. Soft edges, such as hair, and out-of-focus edges are pulled quite easily with the Keylight node. To ensure the best results, try to always pull the key on raw plates. In the Keylight parameters, there is a colourspace control to indicate if the plate is in log, linear, or video color space. Therefore, you should not perform color correction on film plates when feeding the plates into Keylight. For a hands-on example of using the Keylight node, see Tutorial 5, "Using Keylight," in the Shake 4 Tutorials. Float Support in Keylight The Keylight node now supports the preservation of 32-bit data. As a result, float images may require different keyer settings than 8-bit images. For example, highlights in the foreground subject of float images may produce unexpected areas of translucency due to barely perceptible green or blue casts that are preserved in float, but which would be clipped in 8 bit or 16 bit. This can be addressed by lowering the highlightGain parameter (to approximately -0.25) to strengthen weak areas in the interior of the key. Parameters This node displays the following controls in the Parameters tab: output You have the option to do your composite within the Keylight node, but there are other output options as well should you want to composite the foreground image using other nodes: • comp: Renders the final composite, against the assigned background. • on Black: Renders the foreground objects over black, creating a premultiplied output. • on Replace: Renders the foreground objects over the replaceColour. This is a good mode to test your composite. Choosing a bright color allows you to instantly see if there are unwanted transparent areas in the foreground subject. • unpremult: Renders the foreground without premultiplying the matte. Use this mode when you want to add transformations and color corrections after pulling the key. You then apply either a MMult node or enable preMultiply in an Over node to create the final composite. 706 Chapter 24 Keying