Macintosh Reference Guide

Taking Screen Shots

Last updated Aug 5, 2005.

Have you ever wondered how a writer such as myself takes all those crisp, clear screen shots that accompany my articles? Even though you may never need to write illustrated technical documentation, there are plenty of reasons why you might want to take a screen shot every now and then. Perhaps your grandparents need a visual reminder of which button to click in Mail to delete spam, or maybe you want to capture an error message so you can repeat the exact wording to a technical support representative. Heck, you might even want to play a simple but dastardly trick on a coworker (I'll explain how momentarily).

Screen Capture

One way to take screen shots is to invoke Mac OS X's built-in screen capture capability by pressing the following keyboard shortcuts:

• Command-Shift-3: Immediately takes a picture of the entire screen.
• Command-Shift-4: Changes the cursor into crosshairs. Drag the crosshairs over a section of the screen, then release the mouse button to capture the shaded area.

By default, screen shots captured in this fashion are saved as PNG image files on the Finder's desktop, sequentially named Picture 1, Picture 2, etc. To copy the image to the Clipboard instead, hold down the Control key when you press the appropriate keyboard shortcut.

Those are the basic methods of capturing screen shots, but you can get a little fancy when necessary. Suppose you want to take a picture of just one window, only the menu bar, a particular menu, or some other distinct screen element? After all, extraneous items in the background will distract your audience's attention if you're trying to focus on only one particular thing. You could use Command-Shift-3 to snap the entire screen and then manually edit the resulting image file, or you could use Command-Shift-4 and try to meticulously select only the portion of the screen you want. Better yet is to press Command-Shift-4, then press the spacebar. This changes the cursor from crosshairs to a camera. As you move the camera cursor over screen objects, they are highlighted. When the item you want is highlighted, click it and the captured image will contain that precise item with no unsightly extra pixels around the edges.

Are you ready for the trick I promised to show you? OK, here goes. When your victim leaves his or her Mac unattended, press Command-Shift-3 to take a picture of the entire screen in its current state (ideally there will be a bunch of windows open with buttons displayed). Open Desktop & Screen Saver preferences, and make the Picture 1 screen shot the new desktop file. Deselect the "Change picture" check box so that it never picks another image, then close Desktop & Screen Saver preferences. Sneak away and wait for the sounds of befuddlement when your victim starts wondering aloud why the onscreen windows can't be closed, buttons don't react when clicked, and icons can't be dragged. Of course none of these screen elements function properly because they exist only as part of the image file decorating the desktop. After you've had your fun, revert Desktop & Screen Saver preferences to their previous settings.

Grab

Mac OS X's built-in screen capture functionality is sufficient for most needs, but there's one task where it fails entirely: taking shots of items that can't be viewed on screen—such as pop-up menus or the screen saver—while you're pressing the keyboard shortcut. For that, you need to resort to Grab (/Applications/Utilities).

If you open the Capture menu (see the following figure) in Grab, you'll see options that duplicate the basic functionality of Mac OS X's built-in screen capture.

Choosing Capture > Selection (Shift-Command-A) is essentially the same as pressing Command-Shift-4 in that both allow you to select a portion of the screen to capture. The only difference is that when invoked using Grab, a dialog appears explaining how to proceed, and a tool tip pops up next to the cursor. Initially the tool tip shows the position of the cursor in pixels, and then when you begin to drag, it shows the size of the selection rectangle. Once you've made your selection, it appears in a document window within Grab, giving you a chance to check it before saving it as a TIFF file (use the Preview application to convert your screen shots to other formats if necessary).

The other Capture menu items work in much the same way. You choose from the menu and a dialog instructs you on how to proceed. Personally, I find Grab's user interface too pedantic for everyday use, but occasional users may find it reassuring.

The only time I ever actually use Grab is when I need to take advantage of its unique Timed Screen feature. Choose Capture > Timed Screen (Shift-Command-Z), then click Start Timer in the dialog that appears. You have only ten seconds to get the screen in the desired state (I sure wish Apple made the length of the delay a preference item...oh well), so quickly switch to the application you want, open a pop-up menu if necessary, and then wait. Just before Grab captures the full screen you'll hear a beep, followed by the sound of a camera shutter. This is exactly how I managed to take the screen shots of the Finder's built-in slideshow in last week's column.

Grab and Mac OS X's built-in screen capture capabilities are great free tools if you take a screen shot every now and then, but if your needs are more demanding, then I recommend you check out Snapz Pro X from Ambrosia Software. Billed as "the professional's screen capture tool," they ain't kidding. It costs $69, but it's worth every penny. In addition to offering a wide array of options for static screen shots (eight file formats, scaling, cropping, dithering, borders, thumbnails, watermarks, etc.), Snapz Pro X can also capture full motion video, which is great for creating tutorials. Best of all, Snapz Pro X features a streamlined user interface (see the following figure) that presents its many options clearly, but without getting in the way, which is important when you rely upon it like I do to help produce books and documentation.