Apple Shake 4 Tutorials - Manual (Page 167)

Chapter 5 Using Keylight 167
3 In the Parameters2 tab, boost the Viewer gamma level by typing “2.2” into the
viewerGamma value field.
The heightened gamma level reveals noise in the image. If you lower the
viewerGamma, holes are revealed in the mask. You probably don’t see much until the
value drops below 0.5, so don’t worry about the holes for this composite. However, try
to correct the background noise.
Primatte allows you to combine several pixel samples to allocate foreground and
background color. Keylight, however, relies on sliders and masking to tune the
relationship between foreground and background. In this example, there are two
parameters to help you. (The possibility exists that your mask is fine, by the way.)
Adjusting the Mask With Parameters
The first parameter you can use to adjust the mask is screenRange. Raising the
screenRange value increases the contrast in the mask. This slider is typically used for
garbage masks that are later fed into other masks, as it tends to remove fine detail.
To test the effect of adjusting the screenRange values:
1 In the Viewer shelf, click the VLUT2 button to deactivate the lookup table.
The VLUT2 button changes to VLUT Off.
2 Ensure that the Keylight node is selected in the Node View.
3 In the Keylight Parameters1 tab, set screenRange to 0.3.
The mask is filled, but the edge quality degrades.
viewerGamma = 1 viewerGamma = 2.2