You can use the Enlarge and Reduce buttons in the Effect Editor or the Effect Preview Monitor toolbar to zoom in or out on an image in the Effect Preview monitor.

This allows you to view parts of an image in detail or to view parts of effects and effect controls that extend beyond the limits of the standard-size image. For more information, see Effect Editor Controls. and Understanding the Effect Preview Monitor.

When you use the Enlarge button to increase the size of the image in the Effect Preview monitor, you cannot view the entire frame all at once. When you are creating an effect that requires great detail, you can reposition the enlarged frame in the monitor to view the sections that need your attention.