Adobe Premiere Elements 8 - Manual (Page 186)

181 USING ADOBE PREMIERE ELEMENTS 8 EDITOR
Applying effects
Last updated 8/12/2010
Alpha Adjust
A. Clip with alpha channel B. Ignore Alpha C. Invert Alpha D. Mask Only
More Help topics
“ Invert or hide alpha channels ” on page 165
Blue Screen Key and Green Screen Key
The Blue Screen Key effect and the Green Screen Key effect create a keyhole of all clip pixels that are similar to a
standard blue screen or green screen, so that they become transparent. This effect is typically used to replace a blue or
green background with another clip, as in replacing a blue screen behind a TV weatherman with a weather map.
Effective use of the Blue Screen Key or the Green Screen Key requires footage where the background is a bright, evenly-
lit standard blue or green screen. Make sure that persons or objects you place in front of the backdrop don’t match the
color of the backdrop (unless they have areas that you also want to make transparent). For footage with a single-color
background that doesn’t match these requirements, try Chroma Key or the Videomerge effect.
You can adjust the following settings in the Properties view of the Tasks panel:
Threshold Sets the level of blue or green that determines transparent areas in the clip. Dragging the Threshold slider
to the left increases the amount of transparency. Use the Mask Only option to view the black (transparent) areas as you
move the Threshold slider.
Cutoff Sets the opacity of the nontransparent areas that the Threshold setting specifies. Dragging the Cutoff value to
the right increases the opacity. Select the Mask Only option to view the white (opaque) areas as you drag the Cutoff
value.
Smoothing Specifies the amount of anti-aliasing (softening) applied to the boundary between transparent and opaque
regions. Choose None to produce sharp edges, with no anti-aliasing. This option is useful when you want to preserve
sharp lines, such as those in titles. Choose Low or High to produce different amounts of smoothing.
Mask Only Displays only the clip’s alpha channel. Black represents transparent areas, white represents opaque areas,
and gray represents partially transparent areas.
More Help topics
“ Superimposing and transparency ” on page 160
Chroma Key
The Chroma Key effect creates transparency from a color or range of colors. You can use this key for a scene shot
against a screen that contains a range of one color, such as a shadowy blue screen. Select a key color by clicking the
Color swatch or by clicking the Eyedropper tool and selecting a color in the Monitor panel. Control the range of
transparent colors by adjusting the tolerance level. You can also feather the edges of the transparent area to create a
smooth transition between the transparent and opaque areas.
A B C D