Apple Final Cut Pro X 10.1.2 User Guide

 Chapter 11    Keying and compositing 3 61
 •Chroma Rolloff: Use this slider to adjust the linearity of the chroma rolloff slope (displayed 
in the small graph to the left of the Chroma control). Chroma rolloff modifies the softness 
of the matte around the edges of regions that are affected most by the Chroma control. 
Lowering this value makes the slope of the graph more linear, which softens the edges of the 
matte. Raising this value makes the slope of the graph steeper, which sharpens the edges of...

 Chapter 11    Keying and compositing 362
 4 Click Spill Suppression to reveal the following controls:
 •Spill Contrast: Use this grayscale gradient to adjust the contrast of the color being suppressed, 
using Black and White point handles (and corresponding sliders). Modifying spill contrast can 
reduce the gray fringing surrounding a foreground subject. The Black point handle (on the left 
side of the gradient control) lightens edge fringing that is too dark for a successful composite. 
The White point...

 Chapter 11    Keying and compositing 363
 •Mode: Use this pop-up menu to choose the compositing method that blends the sampled 
background values with the edges of the keyed subject. There are five modes:
 •Normal: Evenly blends light and dark values from the background layer with the edges of the 
keyed foreground layer.
 •Lighten: Compares overlapping pixels from the foreground and background layers, and then 
preserves the lighter of the two. Good for creating a selective light wrap effect.
 •Screen:...

 Chapter 11    Keying and compositing 364
For the following examples, this speedometer image will be keyed over an outdoor car scene, 
creating a reflected look.
Apply the luma key effect
 1 In the Timeline, move the playhead to the point in the background clip (the clip you want to 
superimpose the luma key clip over) where you want the key to start.
 2 In the Browser, select the part of the foreground clip (the luma key clip with the black or white 
you want to remove) you want to key over the...

 Chapter 11    Keying and compositing 365
 5 Do one of the following:
 •Drag the effect to the Timeline foreground clip to which you want to apply it.
 •Double-click the effect thumbnail to apply it to the selected clip.
The Luma Keyer effect automatically configures itself to remove black video. If the resulting key is 
not right or you would like to improve it, you can adjust the luma key effect.
Adjust the luma key effect
The following steps assume you have applied the Luma Keyer effect.
 1 In the...

 Chapter 11    Keying and compositing 366
 •Composite: Shows the final composited image, with the keyed foreground subject over the 
background clip. This is the default view.
 •Matte: Shows the grayscale matte, or alpha channel, that’s being generated by the keying 
operation. White areas are solid, black areas are transparent, and varying shades of gray 
indicate varying levels of transparency. Viewing the alpha channel makes it easier to spot 
unwanted holes in the key or areas that aren’t transparent...

 Chapter 11    Keying and compositing 367
 3 Click Matte Tools to reveal the following controls:
 •Fill Holes: Increasing this parameter value adds solidity to regions of marginal transparency 
within a key. This control is useful when you’re satisfied with the edges of your key, but you 
have unwanted holes in the interior that you can’t eliminate via the Luma Rolloff parameter 
without ruining your edges.
 •Edge Distance: Lets you adjust how close to the edge of your keyed subject the effect of the...

 Chapter 11    Keying and compositing 368
 •Intensity: Use this slider to adjust gamma levels to lighten or darken the interaction of wrapped 
edge values with the keyed foreground subject.
 •Opacity: Use this slider to fade the light wrap effect up or down.
 •Mode: Use this pop-up menu to choose the compositing method that blends the sampled 
background values with the edges of the keyed subject. There are five modes:
 •Normal: Evenly blends light and dark values from the background layer with the edges...

 Chapter 11    Keying and compositing 369
 3 Select the foreground clip.
In the above example, the light stands need to be removed.
 4 Click the Effects button in the toolbar.
 5 In the Effects Browser, double-click the Mask effect to apply it to the selected foreground clip.
Tip:  Type “mask” in the Effects Browser’s search field to quickly find the mask effect.
67% resize factor     

 Chapter 11    Keying and compositing 370
 6 Adjust the four corners of the mask to crop out the objects you want to remove, in this case, the 
light stands.
When adjusting the mask, be sure to leave shadows and other details that can help make the key 
more realistic later.
 7 Apply the appropriate keyer effect to the foreground clip.
The foreground is composited over the background.
67% resize factor