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davidnave Author

Level 1

10 points

When waking Macbook Air 2012 from the Login Screen, the display flashes, then works normally. Mildly concerned.

I have only noticed this behavior when no users are logged in, and the computer is put to sleep by closing the clamshell. It also only appears to happen after an extended sleep, meaning 30 minutes or more. I open the clamshell, the backlight comes on, I see the login screen, then the screen flashes like when Photo Booth takes a picture, then the computer works normally. This is not a great concern, but it is unusual. It doesn't happen when a user is logged in. It doesn't happen during boot. I am running 10.8.2, and do have power nap enabled. I have noticed the behavior both when running on the power adapter and on the battery. No Accessibility functions enabled. Trying to isolate the issue, and reaching out for others with same behavior. Cheers.

MacBook Air, OS X Mountain Lion (10.8.2)

Posted on Sep 20, 2012 7:45 AM

Top-ranking reply

Jon P D

Level 4

1,522 points

Posted on Sep 20, 2012 11:25 AM

the screen flashes like when Photo Booth takes a picture

Do you have any security software installed? Some have features that take a photo with the webcam when the lid is opened.

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72 replies

NickH2

Level 1

5 points

Dec 12, 2012 2:58 PM in response to davidnave

+1 for Davidnave's suggestion from me too. Early days but the flashing seems to have stopped after removing the original sleepimage file and restarting. If you are stuck on how to delete sleepimage:

sudo rm /private/var/vm/sleepimage....and enter your admin password

Dec 13, 2012 6:41 PM in response to davidnave

I'm glad to see others are concerned by this as well. I also saw this after the upgrade to 10.8.2. I booked an appointment with the genius bar who deleted the same sleepimage file that davidnave mentioned and reinstalled 10.8.2. The issue still persists for me after both of these attempts. I do not have this issue when I am connected to my thunderbolt display.

davidnave Author

Level 1

10 points

Dec 16, 2012 10:20 AM in response to RRFS

I appreciate the recommendation. Onyx is a wonderful tool.

davidnave Author

Level 1

10 points

Dec 16, 2012 10:29 AM in response to da-cam

The flash has returned. Deleting the sleep image definitely affected it for a period. I have discovered for my issue it is definitely loading user preferences during the flashing. The loginwindow.app is already loaded, and the system.log is indicating it is searching for both the display preferences and the trackpad preferences for the primary user. I tested it by changing the display profile for one user, but not the other. It loaded the new display preference after the flash.

Also, I have read some posts, and I think people are commenting on two different issues. My issue is definitely software, and the flash I see is not a backlight or display scramble. I think that would be a more serious issue, and if any of you are having that when opening the clamshell, call Apple. They take driver or firmware issue very seriously. They also released a new display update addressing issues like that.

The flash I see is less serious and is exactly like the flash that Photobooth makes when taking a photo, or the same one you get when you enable screen flash for error messages in Accessibility preferences.

I only see it at the login screen, and only after when logging out of the user whose preferences are being loaded during the flash.

NickH2

Level 1

5 points

Dec 20, 2012 4:38 PM in response to davidnave

And likewise for me after davidnave's tip - the sleepimage delete certainly stopped the problem for a short while but it returned a day later after the MBA had been powered off overnight.

My screen flash is also software rather than (backlight) hardware - a distinct graphics flash when logging out as one user before logging in as another also. Will check to see if the exact same display settings across both user accounts on the MBA has any effect...

papcio24

Level 1

0 points

Jan 18, 2013 11:56 PM in response to davidnave

The problem with flashing screen and delayed start of Mountain Lion seems to be connected with hibernationmode. When you change hibernationmode to "0" the problem disappeared.

Laptops normally have hibernationmode 3 so the data from RAM are copy to disk after 70 minutes of sleep.

When you change hibernationmode to 0 the data will be store only in RAM.

Commend in terminal: sudo pmset -g hibernationmode 0

to check your hibernationmode: pmset -a

Sorry for my english,

Best wishes

davidnave Author

Level 1

10 points

Jan 19, 2013 7:27 AM in response to papcio24

Sounds very promising. I'll change the setting and let you know.

papcio24

Level 1

0 points

Jan 19, 2013 1:01 PM in response to papcio24

My mistake:

To check hibernationmode type in terminal

pmset -g

to change hibernationmode type

sudo pmset -a hibernationmode 0

davidnave Author

Level 1

10 points

Jan 19, 2013 4:12 PM in response to papcio24

Gotcha, read up on the man because that's the sort I am.

I have it set to 0 instead of 3, which is the default. So, we'll see how it behaves.

The value is hibernatemode instead of hibernationmode.

sudo pmset -a hibernatemode 0

then to confirm

pmset -g

sfmanuel

Level 1

4 points

Jan 22, 2013 8:07 PM in response to davidnave

JHooray!!! I have been flicker free for a couple of days now since making this change. Thanks to papcio24 for the workaround and davidnave for the due diligence 🙂

-manuel-

davidnave Author

Level 1

10 points

Jan 22, 2013 8:15 PM in response to sfmanuel

Glad to hear it. I am also very optimistic. No flashes upon wake for several days now. And no sluggishness when waking either. Much appreciated, regardless, papcio24.

Feb 20, 2013 3:39 AM in response to davidnave

Just a warning about setting hibernatemode to 0: as papcio24 mentioned above, hibernatemode 0 means your Mac will only suspend to RAM. That means that if you put your MacBook to sleep and it runs out of battery, you will lose anything not saved and the next time you start up after connecting power, it will not resume from sleep, but boot up from scratch.

Another side effect is that hibernatemode 0 will cause your MacBook to run out of battery slightly faster when sleeping, as the RAM uses energy to maintain its state. Your MacBook will never enter "Deep Sleep" mode.

On the other hand, an advantage of using hibernatemode 0 is that you can delete the /private/var/vm/sleepimage file and it won't be recreated, saving you some useful disk space (4GB or 8GB, depending on how much RAM your machine has).

As long as you're aware of those potential issues, then go ahead. Personally I don't have an issue with the screen flash on my MBA, knowing that it's simplly linked somehow to restoring state from disk (SSD).

Feb 20, 2013 8:15 AM in response to michaelab

Thanks for that, michaelab. I was waiting for someone to post more of an explanation before adjusting the sleep settings on my 2012 MBA. Now that I have a better picture of the hibernatemode effects, I think I'll go ahead and try it (besides, I could use the extra drive space on my SSD!).

For me, this issue cleared-up for a while, but then returned. In addition to the flash, I'm having to wait a while before I can type in my password, plus I see some weird animations of the log-in windows (i.e. growing/zooming-in, then snapping back to normal size). I've often wondered if this issue may have something to do with the fact that I commonly use an external monitor with the MBA lid closed; I thought that the OS was pausing before letting me log-in because it was looking for the active monitor, and thus the reason the screen would flash or have other weird anomolies.

davidnave Author

Level 1

10 points

Mar 2, 2013 9:47 AM in response to klockw243

Agreed, michaelab really fleshed out what's going on. The issue does go away for awhile, but it returns. I am willing to bet that Apple considers it expected behavior, or at least tolerable behavior. I haven't experienced the zooming effect, but I do have the delay before while it loads the image before I can type. I think you're right about the weird animations, klockw243; it sounds like it's switching resolutions on you. On mine, the login window icons will sometimes not render correctly, or the Apple logo overlay will sometimes be missing. More often, I see the Bluetooth Setup assistant window for several seconds before the flash. It hasn't affected performance. I like having that extra 8GB on the SSD, so I think I will keep the hibernation settings as is, and I rarely drive the battery all the way down. I don't use powernap because I could care less about push services during sleep, and I only backup manually. I called Applecare about it, and it is up with Site Support now, which is about as far as a consumer can take it. If they come back with something, I will pass it along.

Apr 2, 2013 1:49 AM in response to davidnave

Just to add that, since I updated to OS X 10.8.3 I haven't seen the flashing issue, so it looks like it might have been fixed in the 10.8.3 update.

When waking Macbook Air 2012 from the Login Screen, the display flashes, then works normally. Mildly concerned.