Transformations, such as rotation and scale, occur around the anchor point (sometimes called transformation point or transformation center) of the layer. By default, the anchor point for most layer types is at the center of the layer.

Though there are times when you’ll want to animate the anchor point, it’s most common to set the anchor point for a layer before you begin animating. For example, if you’re animating an image of a person made up of one layer for each body part, you’ll probably want to move the anchor point of each hand to the wrist area so that the hand rotates around that point for the whole animation.

The easiest way to pan and scan over a large image is to animate Anchor Point and Scale properties.

Alan Shisko provides a detailed video tutorial on his website, demonstrating how to create a complex 3D environment from 3D layers, beginning with simple 2D assets. Manipulating layer anchor points is a crucial part of this tutorial.

Anchor point in center of text layer (left) compared to anchor point moved to the end of the text layer (right)

When you use the Pan Behind tool to move the anchor point in the Composition panel (left), After Effects automatically compensates for the move so that the layer maintains its position relative to the composition frame (right).