Premiere CC: Two Color Chroma-Key

Here’s a chroma-key effect that uses two different colors to allow us to change backgrounds during the same clip.

NOTE: Here’s an article that describes how to create this same effect in Final Cut Pro X.

There are many stock footage clips that use this two-color effect. This is an especially clever technique to use when you can shoot the background clip with a camera; for example, a hand unwrapping a present to first reveal the blue layer, then peel that off to reveal the green layer. This gives the effect of unwrapping a present to first reveal the box, then the contents of the box.

In this example, I’m using blue and green, but any two different colors can be used to create this effect.

Here’s the first layer: A paper layer that page-peels to reveal a chroma-key blue background.

NOTE: Yes, I know. It’s a page peel. But I need to illustrate movement while using still image screen captures. You can substitute a more interesting transition when you create this for yourself.

Here’s the second layer: A blue background peeling back to reveal green.

And here’s the end result: insert one clip into the blue layer and a second clip into the green layer, while retaining the top, paper, layer and all effects.

REMOVE THE FIRST COLOR

First, place the chroma-key clip (the one with the two color backgrounds) on V2.

Then, place the first background clip on V1. In our example, this is a sunset shot.

Open the Effects panel, twirl down Keying, and drag the Ultra Key effect on top of the chroma-key clip. (If the chroma-key clip is selected in the Timeline, you can apply the filter by double-clicking it in the Effects panel.)

Position the playhead in the Timeline so that you can see the first background color.

Open the Effect Controls panel, and click the eyedropper icon next to Key Color.

Click the eyedropper in the first background color, currently displayed in the Program Monitor. Instantly, the blue color is replaced by the sunset shot.

Verify you have a solid key by changing the Output menu to Alpha Channel.

Then, in the Program Monitor, the foreground (paper) should be fully white (opaque), while the background (sunset) should be fully black. If there are holes in the foreground, remove them by twirling down the Matte Generation arrow, and adjusting Transparency until the foreground is solid white.

NOTE: The soft edge on the left side of the white shape is the drop shadow created by the effect. This is a good thing and should be left alone.

Reset the Viewer display by changing the Output menu back to Composite.

REMOVE THE SECOND COLOR

To create the key for the second color, select both the chroma-key and background clips in the Timeline, then choose Clip > Nest.

In the resulting dialog, give the combined clip (called a “nested” clip) a name. You can name this anything that makes sense to you. In this example, I’m calling it “Chroma-key Nest.”

In the Timeline, the two clips are now coalesced into a single nested clip.

Select the nested clip and move it up to V2. (Shortcut: Option+Up Arrow).

Edit the second background below the compound clip. You can trim it so that it starts just before the effect, if you want, but the trimming is not required. I’m doing so here to make it easier to see the differences between the two clips.

Position the playhead so you can see the second background color; again, in this case, I’m using green.

Drag the Ultra Key effect from the Effects panel on top of the nested clip.

Just as we did before:

• Select the Key Color eyedropper, then click directly on the green background displayed in the Program Monitor
• Verify the key looks good by changing the Output to Alpha Channel and make sure the white foreground is solid white
• If it isn’t, adjust Matte Generation > Transparency

Ta-DAH! Done.

SUMMARY

This technique can be used to create a wide variety of very interesting effects, either shot in-camera or created in After Effects.

The key is to create the first key in the Timeline, while the second key is created using a nested clip.

Cool.

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