Locking previews to a specified window (6.5)

When you start an animation preview, the frontmost Composition, Layer, or Footage window is previewed by default. After Effects 6.5 lets you override this behavior and designate any open window as the default window to preview. This is particularly useful when you have a Composition window that represents your final output and you always want to preview that window even when you're tweaking settings in other windows.

When you start a RAM or spacebar preview, the window that's set to always preview is the only one previewed. When you preview to an external monitor, the external monitor displays only the window that's set to always preview. When you preview with tabbed Composition windows, the window that's set to always preview appears frontmost only for the duration of the preview.

To specify a Composition, Layer, or Footage window to always preview:

Click the Always Preview This View button  in the bottom left corner of the window.

To force a window that's set to always preview to remain frontmost when previewing in tabbed Composition windows, interrupt the preview by holding down the Alt (Windows) or Option (Mac OS) key and pressing any key or clicking.