The other day after I had awakened my Mac from sleep, I noticed the sudden and persistent appearance of the display brightness feedback overlay image. The white-colored image normally disappears within a few seconds after pressing one of the trigger keys (F14 and F15 on an Apple Pro Keyboard). Intrigued, I documented this phenomenon by capturing the screen display twice in succession using the keyboard shortcut, Command-Shift-3. I browsed the Console log to search for clues but found none. Finally, I rebooted the computer, and the screen went back to its normal appearance.