Theater Mode is a special operating mode of some iMacs and desktop Macs that use an ADC-equipped 17-inch Apple Studio Display. It brightens movie playback in some QuickTime applications, like iMovie and QuickTime player. Apple has released a new update to its Theater Mode extension which it says improves compatibility issues.
Theater Mode 2.0.3 is an extension for Mac OS 9 that resolves compatibility issues with QuickTime Player 4.1.4 and 5.0, as well as the Classic environment in OS X. Apple recommends that users of Theater Mode 2.0.2 or earlier should install the update for best performance and compatibility.
System requirements call for the U.S. English version of Mac OS 9.1 or later and Mac OS X, an iMac or desktop Mac that uses an Apple Studio Display CRT.