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 
the matte.
 •Luma Rolloff: Use this slider to adjust the linearity of the luma rolloff slope (the ends of the 
bell-shaped luma curve displayed in the Luma control). Luma rolloff modifies the softness of 
the matte around the edges of regions that are affected most by the Luma control. Lowering 
this value makes the slope between the upper and lower handles in the Luma control more 
linear, which increases edge softness in the matte. Raising this value makes the slope steeper, 
sharpening the edges of the matte and making them more abrupt.
 •Fix Video: Select this checkbox to apply subpixel smoothing to the chroma components of the 
image, reducing the jagged edges that result from keying compressed media using 4:2:0, 4:1:1, 
or 4:2:2 chroma subsampling. Although selected by default, this checkbox can be deselected if 
subpixel smoothing degrades the quality of your keys.
 3 Click Matte Tools to reveal the following controls:
 •Levels: Use this grayscale gradient to alter the contrast of the keyed matte, by dragging three 
handles that set the black point, white point, and bias (distribution of gray values between the 
black point and white point). Adjusting the contrast of a matte can be useful for manipulating 
translucent areas of the key to make them more solid (by lowering the white point) or more 
translucent (by raising the black point). Dragging the Bias handle right erodes translucent 
regions of the key, while dragging the Bias handle left makes translucent regions of the key 
more solid.
 •Black, White, Bias: Click the disclosure triangle in the Levels row to reveal sliders for the Black, 
White, and Bias parameters. These sliders, which mirror the settings of the Levels handles 
described above, allow you to keyframe the three Levels parameters (via the Add Keyframe 
button to the right of each slider). Keyframing the Black, White, and Bias parameters may yield 
a better key, one that adapts to changing blue-screen or green-screen conditions.
 •Shrink/Expand: Use this slider to manipulate the contrast of the matte to affect matte 
translucence and matte size simultaneously. Drag the slider left to make translucent regions 
more translucent while simultaneously shrinking the matte. Drag the slider right to make 
translucent regions more solid while simultaneously expanding the matte.
 •Soften: Use this slider to blur the keyed matte, feathering the edges by a uniform amount.
 •Erode: Drag this slider right to gradually increase transparency from the edge of the solid 
portion of the key inward.
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 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 handle (on the right side of the gradient control) darkens edge fringing that 
is too light. Depending on how much spill is neutralized by the Spill Level slider, these controls 
may have a greater or lesser effect on the subject.
 •Black, White: Click the disclosure triangle in the Spill Contrast row to reveal sliders for the 
Black and White point parameters. These sliders, which mirror the settings of the Spill 
Contrast handles described above, allow you to keyframe the Black point and White point 
parameters (via the Add Keyframe button to the right of each slider).
 •Tint: Use this slider to restore the natural color of the keyed foreground subject. Because the 
Spill Suppression controls eliminate blue or green spill by desaturating subtle blue or green 
fringing and reflection on the subject, the Tint slider lets you add hues to restore the natural 
color of the subject. Overdoing this parameter results in over-tinting the subject with the 
complementary color of the hue being suppressed—magenta if green, and orange if blue.
 •Saturation: Use this slider to alter the range of hues introduced by the Tint slider (when the 
Tint slider is used at moderate levels).
 5 Click Light Wrap to reveal the following controls:
 •Amount: Use this slider to control the overall light wrap effect, setting how far into the 
foreground the light wrap extends.
 •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.
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 •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: Superimposes lighter portions of the background layer over wrapped areas of the 
keyed foreground layer. Good for creating an aggressive light wrap effect.
 •Overlay: Combines the background layer with the wrapped areas of the keyed foreground 
layer so overlapping dark portions become darker, light portions become lighter, and colors 
become intensified.
 •Hard Light: Similar to the Overlay composite mode, except that colors become muted.
Animate the chroma key effect
To compensate for changing conditions in the foreground clip, you can make Sample Color and 
Edges adjustments at multiple points in the clip.
The following steps assume you have applied the chroma key effect.
 1 Place the Timeline’s playhead at the start of the clip.
 2 Use Sample Color and Edges (described above) to create a good chroma key.
 3 Move the Timeline’s playhead to a point later in the clip where the lighting or background 
conditions change, resulting in the chroma key no longer being acceptable.
 4 Use Sample Color and Edges to once again create a good chroma key.
 5 To add additional adjustments at other playhead positions, repeat steps 3 and 4 as needed.
 6 To move the playhead between each adjustment point you add, use the Jump to Sample arrows.
When you play the clip, the Sample Color and Edges settings smoothly change from one sample 
point to the next. For even greater control, you can add keyframes for most of the other settings 
in the Keyer section of the Video inspector. For more information about working with keyframes, 
see  Video animation overview
 on page 258.
Note:  Keyframes for the chroma and luma graphs in the Color Selection controls appear only in 
the Video inspector and not the Video Animation Editor in the Timeline.
Use luma keys
Luma keys provide a way to composite a foreground clip over a background clip based on the 
luminance levels in the video. This is most often useful for still images, such as a picture of a logo 
over a black background, or computer-generated graphics.
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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 background, and choose Edit > Connect to 
Primary Storyline (or press Q).
Foreground clip
Background clip
For details about connecting clips in this way, see Connect clips to add cutaway shots, titles, and 
synchronized sound effects
 on page 10 3.
 3 Select the foreground clip in the Timeline and click the Effects button in the toolbar.
 4 In the Effects Browser, select the Luma Keyer effect.
Tip:  Type “keyer” in the Effects Browser’s search field to quickly find the Luma Keyer effect.
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 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 Timeline, select the clip with the Luma Keyer effect.
 2 Open the Video inspector.
The Effects section of the Video inspector shows the parameters available for adjusting the Luma 
Keyer effect.
 3 To reverse the key and remove white instead of black areas of the foreground clip, select Invert.
 4 To adjust the white and black clip values, drag the handles at either end of the gradient 
thumbnail image.
By default, these handles are set to provide a linear key where the luma level linearly controls the 
transparency of the foreground—100% white is fully opaque, 0% black is completely transparent, 
and 25% gray retains 25% of the foreground image. Dragging the white and black controls 
changes the values that result in fully opaque or fully transparent foreground video.
 5 To adjust the softness of the edges, adjust the Luma Rolloff control.
Higher values make the edges harder, removing any partial transparency, while lower values take 
advantage of any anti-aliasing or softness the edges might have.
 6 To help fine-tune the key, use the View options:
Original (unprocessed 
foreground)
Matte (foreground-based 
alpha signal created 
by the keyer)
Composite (foreground combined  with background)
The name of the 
currently selected 
View button
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 •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 enough.
 •Original: Shows the original, unkeyed image.
 7 To leave smoothly aliased text or graphics in the image visually intact, which can improve the 
edges, select Preserve RGB.
 8 To mix the keyed effect with the unkeyed effect, adjust the Mix control.
For information about making advanced luma key adjustments, see the following instructions.
Make advanced luma key adjustments
The following controls are available for use in difficult keying situations or for fine-tuning specific 
problems:
 •Matte Tools: These controls are for refining the transparency matte generated by the previous 
sets of parameters. These parameters don’t alter the range of values sampled to create the 
keyed matte. Instead, they alter the matte generated by the Keyer effect’s basic and advanced 
controls, letting you shrink, expand, soften, or invert the matte to achieve a better composite.
 •Light Wrap: These controls are for blending color and lightness values from the background 
layer of your composite with the keyed foreground layer. Using these controls, you can 
simulate the interaction of environmental lighting with the keyed subject, making it appear as 
if background light wraps around the edges of a subject.
The following steps assume you have applied the luma key effect.
 1 In the Timeline, select the clip with the Luma Keyer effect.
 2 Open the Video inspector.
The Effects section of the Video inspector shows the parameters available for adjusting the Luma 
Keyer effect.
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 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 Fill 
Holes parameter gets. Reducing this parameter value brings the filled area of the matte closer 
to the edge of the subject, sacrificing translucency at the edges. Raising this parameter value 
pushes the filled area of the matte farther from the edge, potentially introducing regions of 
unwanted translucency within parts of the subject that should be solid.
 •Levels: Use this grayscale gradient to alter the contrast of the keyed matte, by dragging three 
handles that set the black point, white point, and bias (distribution of gray values between the 
black point and white point). Adjusting the contrast of a matte can be useful for manipulating 
translucent areas of the key to make them more solid (by lowering the white point) or more 
translucent (by raising the black point). Dragging the Bias handle right erodes translucent 
regions of the key, while dragging the Bias handle left makes translucent regions of the key 
more solid.
 •Black, White, Bias: Click the disclosure triangle in the Levels row to reveal sliders for the Black, 
White, and Bias parameters. These sliders, which mirror the settings of the Levels handles 
described above, allow you to keyframe the three Levels parameters (via the Add Keyframe 
button to the right of each slider). Keyframing the Black, White, and Bias parameters may yield 
a better key, one that adapts to changing blue-screen or green-screen conditions.
 •Shrink/Expand: Use this slider to manipulate the contrast of the matte to affect matte 
translucence and matte size simultaneously. Drag the slider left to make translucent regions 
more translucent while simultaneously shrinking the matte. Drag the slider right to make 
translucent regions more solid while simultaneously expanding the matte.
 •Soften: Use this slider to blur the keyed matte, feathering the edges by a uniform amount.
 •Erode: Drag this slider right to gradually increase transparency from the edge of the solid 
portion of the key inward.
 4 Click Light Wrap to reveal the following controls:
 •Amount: Use this slider to control the overall light wrap effect, setting how far into the 
foreground the light wrap extends.
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 •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 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: Superimposes lighter portions of the background layer over wrapped areas of the 
keyed foreground layer. Good for creating an aggressive light wrap effect.
 •Overlay: Combines the background layer with the wrapped areas of the keyed foreground 
layer so overlapping dark portions become darker, light portions become lighter, and colors 
become intensified.
 •Hard Light: Similar to the Overlay composite mode, except that colors become muted.
Finalize the key
Quite often your foreground image will have objects that you don’t want to appear in the 
composited output. These could be production items like microphone booms and light stands 
or the edges of the chroma key backdrop. Additionally, you might need to resize or reposition 
the foreground object to better fit with the background. As a final step, you can use the color 
corrector to adjust the foreground so that it matches the look of the background.
Final Cut Pro includes effects that you can use for these purposes.
Use the Mask effect
 1 In the Timeline, move the playhead to the point in the background clip (the clip you want to 
superimpose the chroma key clip over) where you want the key to start.
 2 In the Browser, select the part of the foreground clip (the chroma key clip with the color you 
want to remove) you want to key over the background, and choose Edit > Connect to Primary 
Storyline (or press Q).
Foreground
Background 
attached as a 
connected clip
For details about connecting clips in this way, see Connect clips to add cutaway shots, titles, and 
synchronized sound effects
 on page 10 3 .
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 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.
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 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.
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