Superimposing describes the process of overlaying and combining multiple images. Video clips are completely opaque by default, but superimposing them requires transparency. When you make clips on upper video tracks transparent, they reveal clips on the tracks below.
In Premiere Elements, you can quickly and easily make entire clips transparent by using the Opacity effect. In addition, you can apply any combination of opacity, masks, mattes, and keying to modify a file’s alpha channel, which defines the transparent areas in a clip. More advanced keying effects let you make specific colors or shapes transparent.
Titles you create in Premiere Elements automatically include an alpha channel. You can also import files with predefined transparent areas. Applications such as Adobe After Effects, Adobe Photoshop, Adobe Photoshop Elements, and Adobe Illustrator® can save transparency. Not only will the file have an alpha channel, but it will also conform to your project settings. See the respective user guides for information on saving files with transparency.
A channel that defines transparent areas for a clip. This invisible channel exists in addition to the visible Red, Blue, and Green (RGB) color channels.
A setting that determines how opaque or transparent a clip is. (For example, 75% opacity equals 25% transparency.)
Sometimes used as another word for alpha channel; also describes the process of modifying an alpha channel.
A file or channel that defines the transparent areas of a clip. The matte determines the level of transparency in the resulting image. In Premiere Elements, you use mattes in conjunction with the Track Matte Key.
Defining transparent areas with a particular color (color key) or brightness value (luminance key). Pixels matching the key become transparent. Keying is commonly used to replace a uniform background, such as a blue screen, with another image. (In TV, for example, blue screens behind weather reporters are replaced with weather maps.) The Videomerge effect uses keying to automatically define the primary background color as transparent.
By default, clips appear at full (100%) opacity, obscuring any clips on the tracks below. To reveal lower clips, simply specify an opacity value below 100%. At 0% opacity, a clip is completely transparent. If no clips are below a transparent clip, the movie’s black background becomes visible.
In the Applied Effects panel, expand the Opacity effect and drag the Clip Opacity slider to the desired value.
In the Expert view timeline, choose Opacity > Opacity from the pop‑up menu just above the clip. (You may need to zoom in to see this menu.) Click the Selection tool, position it over the clip’s Opacity graph, and when the pointer becomes a double‑arrow icon, drag the Opacity graph up or down.
To fade a clip in or out over time, animate its opacity. If you simply want to fade to black, click the Fade In or Fade Out option in the Applied Effects panel. You can also create transparency by using keying effects.
To make specific areas in a clip transparent, apply a keying effect based on color, matte, or alpha channel. Pixels that match the specified key become transparent.
Color‑based keying effects
(Videomerge, Blue Screen Key, Chroma Key, Green Screen Key, and Non Red Key) Add transparency wherever a particular color occurs in a clip. For example, you can use color‑based keying effects to remove a background with a uniform color, such as a blue screen.
Matte‑based keying effects
(Four‑, Eight‑, and Sixteen‑Point Garbage Matte Keys, and Track Matte Key) Let you mask out areas of a clip with another clip or with areas you specify manually. You can add transparency according to the shape of a mask you position in the clip, or according to the grayscale tones in a file that you use as a matte. You can also use the Track Matte Key effect to make creative composites.
Alpha channel‑based keying effect
The Alpha Adjust Key effect lets you invert or turn off a clip’s alpha channel or convert areas without transparency to a mask.
For more information about keying out colors, see Help.
To automatically create transparency in the background of a clip, apply the Videomerge effect. This effect makes superimposing clips easy.
On Mac OS, the Videomerge dialog is not displayed when you drag a clip with a solid background. To apply Videomerge on Mac OS, drag the clip to the Monitor panel, and then select the Videomerge option. You can also apply Videomerge from the Effects panel.
To create transparency wherever a specific color occurs in a clip, apply a color‑based keying effect. These effects are commonly used to remove a colored background.
Sometimes a color‑based keying effect properly removes a background, but undesired objects still appear, such as a microphone or cable. Use a garbage matte keying effect to mask out those objects. Garbage mattes work well for areas that have clearly defined boundaries but no uniform color to key. Garbage mattes also work well to clean up unwanted artifacts that a color‑based keying effect left behind.
You can use the Interpret Footage command to change how Premiere Elements interprets a clip’s alpha channel throughout a project.
To ignore or invert the alpha channel of only a single instance of the clip, apply the Alpha Adjust keying effect instead.
Invert Alpha Channel
Reverses the light and dark areas of the alpha channel, which reverses the transparent and opaque areas of the clip.
Tip: If you have difficulty identifying which parts of a clip are transparent, temporarily add a bright color matte on a track below the image you are keying. (See Create a colored matte for a background.)