Using Dual Displays on Mac OS X: The Experience

by Milind Alvares

Using Dual Displays on Mac OS X: The Experience

by Milind Alvares on March 24, 2009

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dual-monitorsMost computer users never come in contact with a dual display setup. Those workspaces, are generally restricted to the professional world. However, displays are getting cheaper and cheaper by the day, and even consumers can now afford a dual display set up.

I personally have a white iMac, the first of the Intel breeds. I have always longed for a dual display setup, and have been looking at my options these first few weeks. The first step I figured, was to buy an mini-DVI to analog monitor cable so I could connect my Dell 24 inch monitor to the iMac.

Everything worked well, and the Dell was instantly recognized and an extended desktop was set up. I did have to colour calibrate the Dell to match the iMac. I have used dual displays before, but this was our first of my own. There is a certain way dual displays work with OS X, so I thought I’d share a little goodies and baddies out here in the open.

Main displays and side displays
The concept of dual displays is divided into the main display and the auxiliary displays. There can only be one main display, but up to seven auxiliary displays if you have a completely beefed up Mac Pro. I on the other hand, have the one iMac display, and the Dell 24 inch. I can choose one of these to be my main display, by default it goes to the iMac.

Drag the little white strip to whichever one you want to set as the ‘main display’. Drag the secondary display in relation to its physical location on your desk.

The main display holds the menu bar as well as the dock. There is only one menubar in your entire dual display setup. Any dialog boxes or unassigned applications pop up on your main screen.

The auxiliary displays on the other hand, will not have a menu bar nor a dock. The concept might feel a little alien at first, but once you get used to going back to your main display access many of the functions it’s quite workable. Adobe CS4 apps now have an “Application Frame” mode, which carries the menubar along in a single window frame, but I prefer it the Mac way. There is a utility “DejaMenu“, which brings up the menubar on right click, but that feels a little excessive.

Wallpapers and screensavers
Each display has a separate wallpaper. The moment you go to your wallpaper preferences, the window will show up on both screens. The best way to have an extended wallpaper is to make two halves using your image editor, and setting them as separate wallpapers. The screensaver on the other hand is the same for all screens, but it is rendered individually so you get different patterns on each screen. This is very taxing on the GPU so it’s best if you use a light screensaver.

You have to manually cut wide images to set it on each desktop.

Finding dual screen wallpapers on the other hand is a difficult task. StudioTwentyEight has some gorgeous free desktops, while Vlad Studio makes dozens of dual screen optimised wallpapers (but they’re for registered users only).

Video Watching
One of the most frustrating things about dual displays on Mac OS X, is that Front Row as well as any QuickTime movie you go full screen on, will show on the primary display. The secondary monitors will go blank. So if you have your Mac hooked up to an HDTV, you will have to set that as the main display every time you want to see some Front Row action there. You can however use iTunes or Quick Look to go full screen on a secondary display. You cannot however do any work on your other display (doing so will bring it out of full screen mode). I’ve heard VLC does better in this regard.

Spaces and Exposé
Spaces works just as you think it would. The concept works without regard for your dual displays. So each space is actually two displays. The Spaces View shows up only on your main display though. That said, I generally prefer to turn off Spaces, as working with dual displays gives you enough space to clear any possible clutter.

Spaces view in dual displays

Exposé also works similarly, but windows on each display stay there. Dashboard also shows only on the main display, but the widgets come flying in from all sides. Looks super cool.

Extended Display on Notebooks
Is best not done. Having the screens in two separate places and dimensions can prove to be quite a pain. Pixel density is also higher on a notebook screen, so moving around feels weird.

The only scenario I can see working on a dual display with a notebook is with something like Aperture or Adobe apps, which are optimised for dual displays. Otherwise it is best to use just one display (either the primary or external) when it comes to notebooks.

The Best uses of Dual Displays
Dual displays are addictive. Once you get used to all that extra space, it’s tough going back to single screen. If you’re into photography, nothing beats the dual display support of Aperture and Lightroom, which have a lot of UI optimizations for the second display. With Adobe apps as well, if you create a new window for the same document, you can have a zoomed out version on your second monitor, while working on the nitty gritty details on your main display. Oh, and for all of this, it is best to have the graphics horsepower of a Mac Pro, as rendering two displays takes a toll on display performance.

Dual displays in Aperture works very differently. Great if you have a MacBook presenting pictures to a client on a large display

Music and film editors love dual displays, the extended timeline allows you to edit much more data at a time. In these cases of course the window is usually stretched across the two displays (and it’s best to have the same sized displays).

For daily usage I loved working on something in Coda while having the browser open on the second display. I could also shove in the Eventbox hud on the secondary display without losing out on screen real estate. It’s situations like these where those apps like CoverStream become totally useful and look awesome. It is very easy however to get lost sometimes, trying to find the mouse on both desktops. I found this free utlity “Mouse Locator” from 2Point5Fish which shows a beacon around the mouse pointer whenever you press the key combo.

That’s it for now, as I still explore the beauties of dual displays. One thing’s for sure though, your desktop looks formidable. Add to that a tiny iPhone and your ‘professionalism’ is heightened to the power of ten!

{ 22 comments… read them below or add one }


I’m pretty sure both Quicktime and DVD Player have a check box in the preference pane to allow them to remain in full screen whilst the application is running in the background.


Milind Alvares

Oh thanks for that! Although, Quicktime still goes fullscreen on the main display only.



Milind, the QT Pro preferences has an option for that.



With QTPro, you can select which monitor you want the video to play in full screen.



Just what I was looking for. :-)



When using Keynote the Large screen shows the presentation as you see it when projected on the second screen it shows the presenters view, time and next slide. Which is ind of nice. Also I found out that if you do certain things (Like geektool your screen) it stays on the larger screen and you need to tweek your main one.



It would have been really nice of you to test VLC to see if that information is true or not and if true, explain to us how it works. It’s still not too late for that, thank you.


Laura Carpenter

Another options for a cursor locater is OmniDazzle (also free) from The Omni Group. It also helps locate your cursor and does much more. I love my pixie dust!



I really have no idea why you think extended desktop on a laptop and external monitor is “best not done”. i do it all the time. Works just as well as multiple displays on an iMac or Mac Pro which I also do.



Extended desktop on a laptop and external display works quite well for me. Just about as well as with an iMac or Mac Pro which I also do. i don’t get why you think it is so much trouble.


Dave is a great resource for dual and triple screen desktop images.

The best way to find them is to browse through the archives.



Great read. We use a dual display set up here at work, but in a different way than described here. We support multiple operating systems in our customer support department. So in our dual monitor set up, the iMac screen is our OS X box and the external Dell monitor is running WinXP in full screen mode. It’s funny the number of people that come by looking for a PC tower somewhere on my desk and I tell them that it’s all coming from my Mac.



Nice. I’ve always been confused about how wallpapers work on a dual display. Helpful comments as well!



It wrks in VLC. There’s an option under video settings.



My MacBook Pro runs a 42″ HDTV with no problem. Great read, thanks.



I’ve got two Apple 24″ Cinema displays, one bought with my Mac Pro about 18 months ago, the second just before Christmas. I was seriously shocked to discover a major colour difference between the two monitors. As a film editor its a real pain. I’ve tried professional screen calibration but even the guy at the Apple store said it was unlikely to work. He said the time between buying the two screens means it was likely there would be a colour difference, even though they’re the same product. So if you’re going to invest in a dual screen set up, and colour continuity is important, then it would seem you have to buy both screens at the same time!



Is it possible to have two separate macs, one sharing the screen with the other mac, but then have one of the computers act as a dual display for the other computer?

Any help will be appreciated. Thanks!


Mr. Man

Yep, it’s pretty easy, you just need ScreenRecycler and a VNC client on the secondary Mac. You can even use it with an iPhone or iPad if you like.



Ok, here’s the deal-

VLC works fullscreen on other screen, just go to preferences/video and turn off the black background

Quicktime and DVD player work, go to preferences/fullscreen settings, “remain in fullscreen when player is inactive”

Thanks for the original article!


Mr. Man

I personally use two monitors with a notebook (Alum MacBook late ’08 13 inch) and it feels fine moving between and such. one thing I do not like though is that I cannot show GeekTool geeklets on both screens.



what do i need to buy to have a double display on my mac mini??



One thing I find lacking in OS X a la mac world is that you cannot change the primary desktop to an external display. Thanks for the ADejavu app though I must try it.


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