I have a new 5K iMac and I'm struggling to find a way to turn off the screen but not sleep the PC. I'm using Option-Command-Eject to turn the screen off, but if I have for example, some things downloading when I do that, then when I press a key to turn the screen back on the download bar won't have moved. I've set Prevent Computer from Sleeping when display is off to ON, but the problem persists. Is there any way to fix this? Thanks all.