Changing an object's duration between explicit and implicit

The duration of an object or composition is determined by its start and end points. The start and end points mark the frames at which the object or composition appears and disappears. When the animation reaches the object's or composition's start point, the object or composition appears. When the animation reaches the object's or composition's end point, the object or composition disappears or stops.

The Explicit/Implicit button lets you switch between two types of duration for objects and the composition:

• An object with an explicit duration exists for the amount of time indicated by its duration bar in the timeline. The object's duration is unaffected by changes made to other objects or to the composition's duration.
• The duration of an object set to implicit length is linked to the length of the composition, to the end handles of other objects, or to the position of its own keyframes. In other words, an object with an implicit duration remains visible in the composition for as long as necessary.

End handle of duration bar set to explicit duration on the left, and implicit duration on the right

To set an object's start and end points:

1. Select the object whose duration you want to change. (Shift-click to select multiple objects.)
2. In the timeline, drag the duration bar or the start and end handles at the ends of the duration bar to change the times at which the object appears and disappears from the animation.
• Drag the start handle to change the object's start time.
• Drag the end handle to change the object's end time.
• Drag the middle of the duration bar to change both the start and end times while maintaining the object's duration.

The duration bar controls an object's life span.

To specify whether an object's duration is implicit or explicit:

Click the Explicit/Implicit button at the bottom left of the Timeline window. When the button is not pressed, it is set to implicit; when the button is pressed, it is set to explicit.