Filed under: Mac 101
Mac 101: curing multiple-monitor mixups with Detect Displays
More Mac 101, tips for the Mac beginner in you. Lucky dual-monitor users, rejoice -- with that second display on your desk, you're bound to be the productivity envy of the entire office. Just one little problem, though: sometimes your Mac has trouble recognizing that extra real estate, and rebooting every time your resolutions get munged is beginning to get old.Relax, and check out your mini-menu for monitors over there in the menu bar. See "Detect Displays?" That's your buddy, right there -- it will tell your Mac to recheck the connected monitors and adjust resolutions as needed. Note the model number of the external display shown; if everything's connected as it should be, your Mac should autosense the type and capabilities of the display without any intervention.
For an even quicker trigger on display detection, try Cmd-F2 (brightness up) on your built-in laptop keyboard. Cmd-F1 will toggle display mirroring, also handy in a pinch.
There are several ways other ways to get external displays to behave; the oldest, for laptop users, is to sleep the machine and wake it back up -- this usually triggers a display detection when all else fails. There's also a Detect Displays button in the Displays preference pane.
Also, to answer a reader question from the comments: it's easy to specify which display acts as the primary monitor in a dual-display setup: just drag the teensy proxy menubar from one display to the other, and your menus, drive icons etc. will follow.
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Reader Comments (Page 1 of 1)
atuck said 1:20PM on 4-07-2008
I've been meaning to write in about a bug that had me stumped for a while invloving multiple displays. At work I have a crappy 19" LCD that is a backup for my 15" MacBookPro. At home I use a 23" Cinema display as my main display and use the laptop as a secondary display. I noticed however, that at work I could NEVER keep my background on my secondary LCD to stop rotating through my wallpaper folder, no matter how I played with the settings.
Turned out that I had to change the settings when I plugged myself back into the 23"er back home in order to change settings for my backgrounds at work!!! Apparently the Cinema display's preferences somehow overpowered the preferences of the crappy 19" dell LCD. Somewhat seemingly appropriate, but annoying nonetheless, as I had some backgrounds a bit too dorky for me to want to display them at work.
So that's another little tidbit in case someone has been dealing with that problem. This is probably not the best place to bring it up, but its loosely related I suppose.
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Peter Zich said 1:38PM on 4-07-2008
Mirror toggling is also F7 on laptops.
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Frank said 1:58PM on 4-07-2008
Score one for TUAW using "munged"!
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Matt B said 2:08PM on 4-07-2008
I have a Mac mini in my living room that I use exclusively as a media player/server. It is connected to my plasma TV via DVI/HDMI which is switched by my AV receiver. I use my Mac mini a few times a week to watch DVDs or listen to music through Front Row and the rest of the time I am watching my cable box, also HDMI switched through the receiver.
Trouble is whenever I switch the receiver to my Mac mini, it does not detect my TV. I have to unplug the DVI cable from the back of the mini and plug it back in to get it to detect the TV. Crawling on my knees and pulling out my components gets annoying when I should just be able to hit a button on my remote to change sources. Does anyone know of a fix? This article sounds like it is in a similar vein.
My mini is set not to go to screen saver, sleep mode, or turn off the display after any period of inactivity. It is set to disable hard drive when possible.
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Ian said 2:32PM on 4-07-2008
I'd be really happy if they fixed that bug that causes my MBP to forget what monitor is attached during a reboot, so that the external monitor is just a munged up mirror of the desktop, instead of a smooth extended part of the desktop.
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Thayne Miller said 3:02PM on 4-07-2008
I've never had this problem. My mbp remembers exactly the settings I've used every time, even under windows.
Maybe it's your monitor.
Ian said 4:26PM on 4-07-2008
Well, it's a Dell 2407 WFPHC, and Leopard does recognize it properly when I do the "Detect Displays" option (just not on reboot).
Matt's comment (#4) made me wonder about something though. My monitor is HDCP compliant, much like his plasma must be, so maybe the digital "handshake" required by HDCP devices is causing the issue.
Channer said 2:59PM on 4-07-2008
@Matt B: same problem here. I'm using a Sony STR-DG800 and I think the HDCP stream is the culprit. If you switch to the cable box HDCP syncs, but the Mac Mini doesn't do HDCP when the receiver or TV expects it.
I have a problem with a 17" MacBook Pro that no longer recognizes a 30" display. It was connected to a projector, and ever since it won't recognize the 30". The screen goes blank for a moment, but never outputs video to the 30". I zapped the PRAM, used the Detect Displays trick and no luck. Going back to the projector it will display video, so I tried moving the menu bar back and forth and no luck. Any ideas?
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aaronL said 4:32PM on 4-07-2008
I have an interesting problem when i restart my computer WITHOUT my external monitor plugged in. At home I have a 21" Samsung as my primary monitor, but when Im on the go, and i startup the computer, it ALWAYS thinks its still connected to the external and I have to manually detect displays to get it to realize there is no monitor plugged in.
Any body with a similar issue?
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Phil said 5:04PM on 4-07-2008
I've had a problem lately (seemed to coincide with 10.5.1 -> 10.5.2 upgrade) where if I restart my MBP and leave the external monitor (old 20" Gateway CRT) the external monitor will just be black, and OS X will insist that it's connected, even if I disconnect/reconnect the cable or do a "detect displays." I always end up having to restart with it disconnected and plug it in again after OS X boots. Anyone else seeing this issue?
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Desmond said 5:10PM on 4-07-2008
TUAW . . . I've JUST started to encounter this problem . . . great timing. I'm running a 15" MBP (2.6 GHz Core 2 Duo) and a ViewSonic VP930b. WITHOUT FAIL, every time I show up at work in the morning and boot cold, it NEVER recognizes the display. I've got to play around and muck about until something finally clicks.
I'll try your suggestions the next time it happens.
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Jody said 6:15PM on 4-07-2008
I assume that the example in this post is two monitors that are being powered off a MacPro desktop.
Anyone have a good solution for a MacBook Pro to be able to power two monitors and have the full screen real estate (not just mirror)???
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Michael Rose said 9:33PM on 4-07-2008
Jody -- the example is a MacBook Pro. You can display 2 different screens without mirroring by simply unchecking "Mirror Displays" under the display menu.
rosciol said 1:41AM on 4-08-2008
Pet peeve about mac laptops. With a PC laptop, even with the lid open, I can make the "secondary" monitor my primary display and the laptop display an extended part of that desktop. For an Apple laptop, my only option is to leave the computer closed in order to use an external monitor as the primary. This doesn't make a lot of sense to me in a variety of situations: with a projector, in the likely scenario where the external monitor is much larger, when I want to have access to the keys/trackpad but not have the laptop screen on.
Why is such a simple piece of functionality missing? Does anyone know how I can: close the lid without putting my mac to sleep, make an external monitor primary with the lid open, and/or turn off/on the laptop monitor while the lid is open?
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Zachary Berry said 12:45PM on 4-08-2008
yes - it's weird, but if you put the macbook to sleep, then plug in the external monitor, THEN plug in a usb device, the machine will use the external monitor but keep the laptop screen off. Then you can open the lid of the laptop and use the keyboard without having the laptop screen turn on.
I just recently found this out myself.
Ralph said 7:18AM on 4-08-2008
Recently switched to Mac and adore my MPB. The one-button mouse and anchors only on one corner of the window are flatly stupid - sorry, but you know it's true. But everything else about this machine is a dream. My only wish: to run multiple external monitors off my MBP. No dualhead2go is not an option because of the restriction to 58 Hz. But Ill name my first-born after whoever points me in another solution!
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