Configuring Display Preferences

If you stare at your display screen for hours on end, you want the view to be crisp and easy on the eyes. If you work with color, you want your screen to display colors as accurately and consistently as possible. If you work with more than one display screen on your computer, you need to have control over how the two work together. If your display is not a flat-panel type, you can set up a screen saver to protect the display against image burn-in.

Toward these goals, you can adjust your display by using the Displays and Screen Saver panes of System Preferences. You can also make quick adjustments with the Displays menu icon.

Like the Date & Time preferences pane, the Displays preferences pane is divided up into several panels, which are accessed via buttons at the top of Displays preferences pane. Depending upon your hardware configuration, the Displays Preferences may provide some or all of the following panels:

• Display: Settings for screen resolution, number of colors, refresh rate, contrast, brightness, and Finder menu bar access.

• Geometry: Settings for adjusting the shape and position of the screen image (not present for all makes and models of displays).

• Color: Settings for selecting a color profile and calibrating your display.

• Arrange: Settings for adjusting how multiple screens work together (present only if you have more than one display and your computer can work with them independently).

Display panel

Click the Display button to adjust the resolution, number of colors, refresh rate, contrast, or brightness of your display, as shown in Figure 13-10. You can also change a setting to show or hide the Displays icon in the menu bar. Some settings are not available with some types of displays. For example, no contrast setting for the LCDs (liquid crystal displays) is used in PowerBooks, iBooks, and flat-panel displays.

Figure 13-10: When using an iBook or a PowerBook that is attached to an external monitor, use the Detect Displays button to have OS X recognize that display.

Resolutions and colors

The two most basic display settings are resolution and number of colors. Resolution is the size of the rectangular screen image — the number of pixels (picture elements or dots) wide by the number of pixels high. The number of colors, often called color depth, is the number of different colors that can be displayed for each pixel of the screen image. Color depth is sometimes referred to as bit depth, which is a measure of the amount of memory it takes to store each pixel (more colors require more bits of memory per pixel).

The higher the number of colors, the more realistic the screen image can look. However, increasing the number of colors doesn’t necessarily make the screen display better, because the picture displayed onscreen may not make use of all of the available colors. For example, a black-and-white photograph is still black, white, and shades of gray when displayed on a screen capable of displaying millions of colors per pixel.

Although you are provided with three choices, for all intents and purposes you have two practical choices of color depth in Mac OS X: thousands or millions of colors per pixel. Mac OS X can’t accurately render its Aqua interface with a lower color depth. However, some old Classic applications may require a color depth of 256 colors.

The settings for resolution depend on the capabilities of the display and the computer’s video card, but in general range from 800 x 600 pixels (the size of the original iBook display) up to 1900 x 1200 pixels (the size of a 23-inch Apple Cinema Display). Some displays can show only one resolution, while most new displays can show multiple resolutions.

Resolution and number of colors are related because increasing either requires more video memory. If you increase the resolution, Mac OS X may have to automatically reduce the number of colors. Conversely, you may be able to set a higher number of colors by decreasing the resolution.

Refresh rate

The significance of the refresh rate setting gets into the mechanics of displaying an image on the screen. The video card sends the screen image to the display one thin line of pixels at a time. After the video card sends the last line, it starts over again with the first line. The refresh rate is a measure of how fast the video card sends lines of the screen image to the display. A higher refresh rate means the entire screen image gets redisplayed more often. The refresh rate is of concern on a display with a CRT (cathode ray tube, or picture tube). If the refresh rate is below about 75 Hertz, the CRT’s glowing phosphors may fade perceptibly before they are refreshed. Your eyes perceive this as a flickering of the video image, and the flickering can lead to eye fatigue and headache. A display with an LCD (liquid crystal display) doesn’t flicker regardless of the refresh rate.

Each make and model of display has certain combinations of resolution and refresh rate that produce a clear, bright image with minimum flicker. If you set the refresh rate to a value that is not recommended for the display, the image probably is distorted or dark.

Tip

When used in conjunction with an LCD monitor some choices of settings for resolution, colors, and refresh rate are dim to indicate they are not recommended. If you want to choose one of these, deselect the checkbox labeled Show modes recommended by display. If you choose a mode that is not recommended, an alert appears in which you must click the Confirm button to retain the mode. If you do not click Confirm within 10 seconds, Mac OS X automatically reverts to the previous mode. This automatic reversion is necessary because some modes may cause the display to show a distorted or black image, which prevents you from reverting to the previous mode by yourself.

Display settings in the menu bar

Besides using the Displays preference pane to adjust the resolution and colors of your display, you can also enable a Displays menu in the Finder’s menu bar. Do this by placing a check mark in the box adjacent to Show displays in menu bar. A pop-up menu allows you to select how many choices are presented in the Displays menu. The increments are 0, 3, 5, and 10. After you’ve enabled it, you can click the Displays icon in the Finder’s menu bar to see a menu of available screen resolutions and numbers of colors. This menu lists all your displays and has a command for turning mirroring on or off. The menu also has a command for opening the Displays pane of System Preferences. Figure 13-11 shows the contents of the Displays menu on an iBook.

Figure 13-11: Use the Displays menu to directly open the Displays preferences pane without having to first open the System Preference application.

Tip

You can move the Displays icon by pressing the z key and dragging the icon. Drag the icon left or right to change its position relative to other icons on the right side of the menu bar. Drag the icon off the menu bar to make it vanish in a puff of smoke.

Geometry panel

With some displays, such as the built-in display of an iMac or an eMac, the Displays preferences pane has a Geometry panel that allows you to adjust the shape and position of the image seen on the screen. You can expand the display area, so that less black border is visible. You can also change the pincushion (how concave the sides of the picture are) and the rotation of the display. Figure 13-12 shows the settings you see when you click the Geometry panel in the Displays preferences pane on an eMac.

Figure 13-12: If your screen image isn’t centered, use the Geometry panel to adjust the shape and position of image on the screen.

The graphic buttons on the right side of the panel reflect the various adjustments that you can make. These buttons change according to which setting you have selected to adjust. You can also make adjustments by dragging edges or the center of the small screen; the shape of the pointer tells you which way to drag. If you wreak havoc on your display by experimenting with the geometry settings, click the Factory Defaults button to returns the settings to their factory presets.

Color panel

The Color panel allows you to select a color profile for your display or to calibrate the display. After you calibrate the display, the Mac OS requires you to name and store the new settings as a color profile. Figure 13-13 shows the selections you see when you view the Color panel on an eMac.

Figure 13-13: You can set the display’s color profile or calibrate the display by clicking the Color panel of the Displays preferences pane.

You can create a custom profile for your display by clicking the Calibrate button in the Color panel. A custom profile accounts for your display’s age and individual manufacturing variations. What’s more, you can configure custom profiles for different resolutions, white points, and gamma corrections. With most displays, clicking the Calibrate button opens the Display Calibrator Assistant. The Calibrator walks you through the process that calibrates your display and creates a new ColorSync profile.

Note

If you have an Apple ColorSync display, AppleVision display, or 21-inch Apple Studio Display, then a Recalibrate button may appear in lieu of the Calibrate button. Clicking Recalibrate activates the self-calibrating hardware built into these displays.

Display Calibrator Assistant

The Display Calibrator is actually a stand-alone application that acts as an Assistant (those coming from the Windows world call it a Wizard) that walks you through the process of creating a custom ColorSync profile for your display. If your ColorSync profile accurately reflects the behavior of your display, applications that take advantage of ColorSync can better display images in their intended colors. Similarly, if you have a proper profile for your printer, the colors match when printed — that’s the sync in ColorSync.

You can use Display Calibrator to create a custom profile for your display and your viewing preferences. A custom profile accounts for your display’s age and individual manufacturing variations. What’s more, you can configure custom profiles for different resolutions, white points, and gamma corrections (more on all these terms shortly). Display Calibrator walks you through the process that calibrates your display and creates a new ColorSync profile. Figure 13-14 shows the Display Calibrator’s introduction.

Figure 13-14: Display Calibrator walks you through calibrating a display and creating a custom profile.

Depending upon the type of display being calibrated, the Display Calibrator Assistant takes you through some or all of the following steps:

1. Introduction: Decide whether to use expert calibration settings instead of basic settings. There isn’t much difference to the casual user, but graphics professionals who use ColorSync for color-correct output may find it useful to select Expert Mode before moving on to the next step. (Expert mode gives you more granular control over the settings in Display Calibrator, although for all intents and purposes it doesn’t change the operation of the Display Calibrator dramatically.)

2. Set Up: Set your display to its highest contrast setting and then adjust the brightness. A test image helps you find the proper setting. This step is omitted on some displays.

3. Native Gamma: Provide information about the display’s current gamma correction. Gamma refers to the relationship between the intensity of color and its luminance. Gamma correction compensates for the loss of detail that the human eye perceives in dark areas. In regular mode, you make adjustments to a gray image; in Expert mode, you determine the current gamma by adjusting sliders until red, green, and blue test images look right. This step is omitted on some displays.

4. Target Gamma: Specify the gamma correction that you want the display to use:

   • 1.8 is the standard gamma for Mac displays.

   • 2.2 is the standard gamma for television displays, video editing equipment, and Windows computers.

   • Native is gamma that is determined between input voltage and display brightness. Typically this feature is not available with LCD displays due to the fact the backlight runs at a constant level of illumination.

   A low gamma setting makes colors appear more washed out. A high gamma setting makes colors appear more brilliant and with higher contrast. In this step, the Expert mode allows you to use a slider to choose a very specific gamma setting.

5. Target White Point: Select your preferred white point, which determines whether colors look warm (reddish) or cool (bluish). You can also choose to make no white-point correction. In Expert mode, you can use a slider to choose a specific white point measured in degrees Kelvin, which is a temperature scale commonly used in science.

6. Name: Name and save the custom profile for future use.

7. Conclusion: Close the Display Calibrator Assistant and select your newly created display profile under the Display Profile menu in the Color panel.

You can repeat the calibration process to create a number of profiles if you use your display at different resolutions or for different purposes.

Arrange panel

If your computer has two displays or more, you may be able to arrange how they work together. In one arrangement, called display mirroring or video mirroring, the second display shows exactly the same image as the first display. The other arrangement treats each display as part of an extended Desktop — as you move the pointer across the Desktop, it goes from one display to the next. Some Mac models, such as the iMac DV, can use two displays only for display mirroring not for an extended Desktop. Multiple displays are configured using the Arrangement panel, as shown in Figure 13-15.

Figure 13-15: Use the Arrangement panel to move the menu bar from one screen to another.

You can change the relative positions of the displays in an extended Desktop by dragging the small screens in Displays preferences. You can also set which display has the menu bar by dragging the little menu bar to the appropriate small screen in Displays preferences. When you have two or more displays in an extended Desktop, Displays preferences has a separate window on each display. Each window has a Display panel, Color panel, and other panel for adjusting the display where the window is located. Only the primary display’s preference pane contains an Arrange panel.

Note

To turn on the display mirroring setting, both displays must be set to the same resolution and number of colors.