Classroom in a book

t
Ignore Alpha
: This makes the alpha 
channel opaque, covering up the clip 
below it.
t
Invert Alpha
: This makes the graphic 
transparent and the alpha channel opaque.
t
Mask Only
: This converts the graphic to a white silhouette.
4
Select Ignore Alpha to see the alpha channel as opaque rather than transparent.
5
Select Alpha Adjust in the Effect Controls panel, and press Delete.
Using video effects that work with 
graphic-file alpha channels
Four video effects work well with graphic-file alpha channels: Alpha Glow, Bevel 
Alpha, Channel Blur, and Drop Shadow. You’ve already seen Drop Shadow, so here 
you’ll use the other three:
1
Choose Video Effects > Stylize > Alpha Glow to apply an Alpha Glow effect to 
the graphic in Video 2; then open its Settings dialog box, and experiment with 
its settings.
The Start Color and End Color parameters set the colors of the glow.

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LESSON 15 Exploring Compositing Techniques
2
Delete Alpha Glow from the Effect Controls panel, choose Video Effects > 
Perspective > Bevel Alpha, and then drag the Bevel Alpha effect into its place.
Give this graphic a 3D beveled feel by adjusting the effect’s parameters.
3
Choose Video Effects > Perspective, and add a Drop Shadow effect below the 
Bevel Alpha effect in the Effect Controls panel. Set Shadow Opacity to 70%, 
Direction to –220, Distance to 15, and Softness to 30, as shown on the left.
Some video formats may also contain alpha channels. DV cannot, but the 
QuickTime.mov and uncompressed .avi formats are examples of formats that 
can contain alpha channels.
4
Drag the scratches.mov clip to the Video 3 track over the logo clip in Video 2 to 
overlay it. Click to select scratches.mov, and then in the Effect Controls panel, 
increase the Scale to 151 so that scratches.mov covers the clips beneath it. This 
.mov clip contains moving scratches and flicker to simulate an old movie. It 
contains an alpha channel that makes the areas where there are no scratches 
transparent, so the content under it can be seen. Play the sequence to observe 
the effect.
5
To enhance the old movie look, drag the brown matte clip to Video 4, and set 
its Opacity parameter to 20%. Press Enter (Windows) or Return (Mac OS) to 
render and play the sequence.