Some tips on getting the job done without pulling out your hair.

Yesterday, I had the pleasure of adding a second display to my 24-in iMac setup. In this quick article, I’ll explain why I did this and provide some tips for how you can do it, too.

Why Two displays?

First of all, you need to understand how having a second display on your computer can work. Basically, you can use the second display two ways:

• Use the second display to mirror the main display. You’d use this primarily when doing a presentation and you need a larger or second display to display to your audience. This is pretty common if you do a presentation from a laptop; you’d connect it to a projector which acts as a second display, then turn on mirroring.
• Use the second display to add screen space to your computer setup. So instead of having the space on one display screen, you also have the space from the second display screen. The joined pair of screenshots below illustrate how this could work. This is how I use the second display.

The following example shows how I use my two displays. The one on the left is my 24-inch iMac display. This is my main display, which includes the menu bar, Dock (when displayed), and desktop icons. The one on the right is my new 22-inch Samsung DVI-D display. I’ve positioned them side by side, so when my mouse pointer is on the right side of the left display screen and I move the mouse to the right, it moves into the right display screen.

You may wonder why, with 24 inches of screen real estate set to its highest resolution (1920 x 1200 pixels), I wanted to add another display to my setup. There are two reasons:

• I could. High resolution digital displays are surprisingly affordable these days (with the exception of those made by Apple and a number of other high-end makers). The new display cost just $309 in Best Buy; and yes, I’m sure I could have gotten a better deal elsewhere, if I were willing to spend days/weeks/months researching and shopping.
• I felt that I could be more productive if I could move my online applications — Mail, Twitterrific, Skype, iChat — into a second display where they’d be visible but I wouldn’t have to switch to them. (Yes, I’ve tried Spaces and I’m very sorry to say that I just couldn’t make it work the way I needed it to with all my apps.)

I would like to mention here that although I bought a Samsung display and it works fine with my iMac, I’m not necessarily recommending it. The picture is okay and it worked right out of the box without installing any drivers. But the picture quality is not anywhere near as good as the incredible picture on my iMac — even my husband commented on it at first glance. So if you work with graphics or have problems with your eyesight and you’re not on a budget, I recommend that you check out an Apple display first. It might just be worth the $900 (for 23 inches) or $1800 (for 30 inches) price tag for you. Personally, I couldn’t justify the additional expense.

Set Up Tips

Once you decide to add a second display, consider these things:

• Can your computer support a second display? This is a biggie. If the answer is no, forget it. You can find out if your Mac can support a second display by visiting the Apple store and chatting with someone working the floor. If that’s not an option, try checking Apple’s Web site for technical specifications on your computer model. (Here’s the specs for mine.) If you’re really confused and your Mac is a currently available model, you can try giving the Apple Store a call at 1-800-MY-APPLE (in the U.S.) and asking. (Please don’t use this phone number to get technical support — it’s a sales number and the person who answers will not be able to help you.)
• What’s the maximum resolution your computer will support for the second display? This is also information you can get from the above sources. You need to know this so you don’t buy a display that’s too big for what your computer can support. My 22-inch Samsung has a lower resolution than what my computer can support.
• What cable will you need for your display? Before you answer this question, either know which display you plan to buy or buy the display. If you’re like me, no matter how many cables and adapters you have in your home or office, you will not have the one you need.

To make sure I got the right adapter, I looked at the description on the display box, examined the DVI-D cable that came with the display, checked the pictures here, called the Apple Store to ask, and looked up the adapter on the Apple Store’s Web site.

Do I sound paranoid? I live 50 miles from the closest Apple Store and there’s nothing more frustrating than getting the wrong cable or adapter. The Apple Web site is full of bad reviews by buyers who bought the wrong adapter; I didn’t want to make the same mistake.

I sent a link to the Apple Store Web page for the adapter to my husband at work in Phoenix and told him to print it and bring it with him to the Apple Store. He walked into the Biltmore store, flashed the printout, and got the right adapter. The cost: $19.

Remember that the adapter I bought works for me with my computer and my second display; it might not work for you. Do your homework and don’t blame me if you buy the wrong one.

Setting Options

Once you’ve got the second display connected and powered up, your Mac should automatically recognize it. Although you may not need to configure it at all, you can. Here’s what the configuration looks like with my Leopard setup.

Open System Preferences and click the Displays icon. Two Displays preferences panes should appear — one on each screen.

Here’s the Display panel of the Display preferences pane on each display. I won’t go into detail on the usual settings; I cover all that in my Leopard book. Instead, note the Gather Windows button. Clicking this button moves all the open windows to that display. You might find this handy if you have a second display connected and you don’t want to power it up. What I’ve discovered is that your Mac will remember where an application’s windows were the last time you ran the application and will reopen the windows there. The Gather Windows button moves those windows to the display you click the button on.

You might also notice a Rotate button on the SyncMaster window for my Samsung display. That’s a weird little feature that enables me to rotate the display’s image in 90° increments. (The larger display actually has a rotating base.)

To set up the positioning of the displays, click the Arrangement button on the main display’s Display preferences pane. The Arrangement panel, shown here, displays the two displays as they are arranged. In my setup, the two displays are physically side by side with the Samsung a little lower than the iMac. You can drag the boxes to reposition the displays and I highly recommend that you do so if you need to. For example, if your second display is on the left, drag its box to the left of the main display. This way the mouse behaves logically when you drag it from one screen to another. (This, by the way, would be a great practical joke to play on a friend with two displays; just switch the boxes around to drive him nuts!)

If you decide you want the menu bar on the other display, just drag it over there. That’ll move the menu bar, Dock, and volume icons that appear on the desktop.

If you want to mirror the displays, as discussed at the beginning of this article, turn on the Mirror Displays check box. This is also where you’d disable this feature if it happened to be turned on by default.

But Wait! There’s More!

Of course, you can set many of the Options in the Displays preferences pane if you turn on the Displays menu. Here’s what my Displays menu looks like with both displays connected. As you can see, I can enable/disable mirroring, set resolution for either display, or open Display preferences. Saves the bother of going into the Displays preferences pane for making minor adjustments.

Learn More

You can learn more about options in the Displays preferences pane on pages 553-554 of Mac OS X 10.5 Leopard: Visual QuickStart Guide.

And if you’d prefer to stick with one monitor, be sure to check out pages 179-183 of the book to learn more about Spaces.