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Lesson 13. Applying Filters > Applying a Key Filter

Applying a Key Filter

Another way to composite two clips is to make a clip's background transparent. This isolates just the foreground of the clip, perhaps a person, object, or graphic, so you can combine it with a different background. This is called a key effect and is created by applying a Key filter. There are two primary types of keys. One is used to key out the luminance of an image area, based on its darkness or brightness. The other is used to key out a particular color, or chrominance, of the image. Final Cut Pro offers several types of key filters. In this exercise, you will explore one that will key out a color in a graphic image.

In the Browser, open the Key Filter sequence.

This sequence has all the filters that have been applied to this point.

To import a new file, press Cmd-I. In the Choose A File window, navigate to FCP5 Book Files > Media > Graphics > Logo FLAT.jpg, and click Choose.

This single-layer JPEG file is displayed in the Browser as a graphic icon, like freeze-frames.

In the Browser, double-click the Logo FLAT.jpg file to open it in the Viewer.

In the Viewer, the graphic has a marked 10-second duration, which is the default setting for still images in the User Preferences. You will edit this clip over the first clip in the sequence. Placing one clip on top of another is called superimposing. To make the graphic duration match the duration of the V1 clip, you will use the Superimpose edit.

In the Timeline, move the playhead anywhere within the CU pan starting line clip. Make sure the v1 source control is patched to the V1 destination control. In the Viewer, drag the graphic image into the Canvas and release it on the Superimpose edit option.

The Logo FLAT.jpg clip is automatically placed on the track above the V1 track and is given the CU pan starting line clip's exact duration. To see the V1 clip, you will have to key out the graphic's blue background.

Double-click the Logo FLAT.jpg clip, and click the Filters tab. Choose Effects > Video Filters > Key > Color Key.


When you want to remove a color from a video image, which is a more complex key, apply the Chroma Key filter.

In the Color parameters, click the Select Color eyedropper button, and then click the blue background in the Canvas. Drag the Edge Feather slider all the way to the left. Drag the Tolerance slider right until you no longer see the blue edge around the graphic.

With the blue background keyed out, you now see the CU pan of starting line clip appear beneath the graphic.

In the Filters tab, click the View pop-up and choose Matte.

With Matte selected, only the alpha channel of the image appears in the Canvas, and you see how clean the graphic key really is.

All video clips are made up of three channels of information: red, blue, and green—or RGB. Images are formed by the combination of these three colors. When you add certain filters onto clips, such as keys and mattes, a fourth channel is created: the alpha channel. Alpha channels are displayed in black and white. The white area is opaque and protects or maintains that portion of the foreground image. The black area is transparent and allows the background image to show through.


To create the cleanest keys in your images or graphics, always take a quick look at the matte of the keyed image. Make sure the white opaque area is as solid as possible so that portions of the RGB background image won't show through.

Adjust the Color Key parameters until the key is as tight around the graphic as possible, and you don't see any black artifacts in the white matte area.

To take an even closer look at the details of this image, click the Canvas Zoom pop-up and choose 200%. Press H to select the Hand tool, move the pointer into the Canvas image area, and drag the image to see other areas of the matte in this zoomed-in view.

When you see an area that has black specs, adjust the parameters in the Key filter until the black no longer appears.

To return the image to its normal size, click the Canvas Zoom pop-up and choose Fit To Window. In the Viewer Filters tab, click the View pop-up again and choose Final.



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