An example of using the pick whip

The following example shows how to use the pick whip to simulate dimming a light bulb while rotating a dial.

Note: To learn what the text in an expression means, see Understanding the expression language.

Linking opacity to rotation:

1. Start with a composition containing two solids: make layer 1 a circle named Light and layer 2 a rectangle named Dial.
2. Create keyframes to animate the rotation of Dial.
3. Select the Opacity property for Light and choose Animation > Add Expression. A default expression appears under the property.
4. Click the pick whip () next to the Opacity expression and drag it to the Rotation property for Dial. After Effects automatically fills in the following expression:

this_comp.layer("Dial").rotation

5. Press Enter on the numeric keypad or click outside of the expression to activate it.
6. Preview the animation. Notice that the Opacity property of Light is animated, yet there are no opacity keyframes.

Note: Make sure to use Rotation values that are compatible with the Opacity property. For example, Opacity values range from 0 to 100, so rotating the Dial layer backward using a negative value results in an Opacity value of 0.