displayimac
I'd like to turn off my iMac display while connected to it via a remote desktop session. I'm using TeamViewer or LogMeIn, and unfortunately the screen stays on during those sessions when it really doesn't need to be on.
Is there any way to set the screen to off while in use?
Note: I don't want to put the display to sleep because that will only last until I start typing or move the mouse.
OS X Lion added per-user screen sharing: the ability to have multiple remote desktop sessions active on a single Mac at the same time. It's not a perfect solution, but you may find it good enough for your case.
When you connect to your Mac via Screen Sharing make sure the session is in Control Mode, not View Mode. You can switch modes by pressing Cmd+Option+X in the Screen Sharing app.
Once in Control Mode, look under the View menu and you should see an entry that says "Switch to Virtual Display". Select that to change the session to a virtual display, not the current desktop display, and log in as yourself.
The main display on your iMac should go to sleep according to your screen saver and energy settings once you've disconnected your remote session from the physical display and moved it to a virtual display.
The only flaw in this approach is I know of no way to start Screen Sharing on a virtual display from the get go. So the initial connect always wakes up the physical display.
Update for Mavericks
The "Switch to Virtual Display" option in the Screen Sharing app went away in Mavericks. Instead, upon connecting to the other Mac with Screen Sharing:
If someone else is already connected to the Mac as a remote user, a dialog asks if you want to share the display with the other remote user (Share Display), or log in concurrently using a different user name and screen (Log In). Choose the option you want.
If you choose Log In, you will share the Mac with the other remote user, but you won’t share the same screen.
Here's an example. In this case I tried to connect a Screen Sharing session from my iMac to my wife's MacBook Pro where she was already logged in. This is the dialog I get when trying to connect:
You can use the pmset command to "ask" power management if there is anything that will prevent sleeping. In this first example, I have recently rebooted, and there isn't anything that should prevent the system from sleeping:
$ pmset -g assertions
5/10/13 8:18:51 AM EDT
Assertion status system-wide:
PreventUserIdleDisplaySleep 0
CPUBoundAssertion 0
DisableInflow 0
ChargeInhibit 0
PreventSystemSleep 0
PreventUserIdleSystemSleep 0
ExternalMedia 0
DisableLowPowerBatteryWarnings 0
EnableIdleSleep 1
NoRealPowerSources_debug 0
UserIsActive 0
ApplePushServiceTask 0
Kernel Assertions: None
Then I started iTunes playing a song. Checking now, you can see that sleep will be prevented by the core audio process.
$ pmset -g assertions
5/10/13 8:19:46 AM EDT
Assertion status system-wide:
PreventUserIdleDisplaySleep 0
CPUBoundAssertion 0
DisableInflow 0
ChargeInhibit 0
PreventSystemSleep 0
PreventUserIdleSystemSleep 1
ExternalMedia 0
DisableLowPowerBatteryWarnings 0
EnableIdleSleep 1
NoRealPowerSources_debug 0
UserIsActive 0
ApplePushServiceTask 0
Listed by owning process:
pid 1124: [0x00000464012c001f] PreventUserIdleSystemSleep named: "Nameless (via IOPMAssertionCreate)"
pid 269: [0x0000010d012c0020] PreventUserIdleSystemSleep named: "com.apple.audio.'AppleHDAEngineOutput:1B,0,1,2:0'.noidlesleep"
Kernel Assertions: None
Best Answer
You can try RedScreen (I don't have an iMac to test it). I read that it can not only decrease the screen brightness beyond OS X defaults (like others do) but also control the screen backlight. You can bypass the default red tinting mode and just use these brightness controls.