Apple released iMac (Mid 2010) Display Brightness Update 1.0 late on Thursday. The update, according to Apple’s scant release notes, “addresses an issue with 21.5-inch iMac (Mid 2010) display brightness.”
The update requires Mac OS X 10.6.4 and weighs in at only 378KB. iMac (Mid 2010) Display Brightness Update 1.0 is free and available for download at the Apple Support Web site.