By Graham K. Rogers

In macOS System Preferences the Displays Preferences panel appears unchanged from previous versions of OS X, although there may have been considerable changes with the Displays preferences files themselves. Panels will differ, however, depending on the specific computer used. The important feature concerning Spaces and presentations is affected by Mission Control preferences.

The Displays panel controls the way screens show content. It has two main sections: Display and Color. For a computer with an inbuilt display, like the MacBook Pro or the iMac, the information will be for the computer's own monitor. This will differ for computers that use an external monitors (Mac Pro, Mac mini). An additional panel - Arrangement - will appear when a (second) external display is connected. This includes a VGA projector, such as those used in classrooms.

Display

The Mac's current desktop picture is displayed. If the desktop is changed (see, Mission Control) and the Displays preferences panel re-opened (or the Resolution settings changed), the picture will change to the new current desktop picture (See Desktop & Screensaver).

There are two Resolution options shown on the right: Default for display and Scaled. Optional resolution icons appear when Scaled is selected or when an external monitor is attached. With earlier versions of OS X, the resolutions were displayed as numbers (e.g. 1024 x 640 - See below).

With the Retina display MacBook Pro the numbers are replaced with small icons, some of which have text descriptions below. When the cursor is placed over an icon, the Mac image on the panel changes to indicate how the display would look. Selecting a new setting changes the Mac icon. When the cursor is held over an optional scaled display setting, a greyed out warning is shown: ""Using a scaled resolution may affect performance" (also see below).

"Default for display" is for users who will want to leave well alone and are content with the setup as provided. When this is selected, there is only a slider for Brightness and a checkbox below this, marked "Automatically adjust brightness." It is still possible to use the slider when the box is checked. When the Function keys (F1 and F2) are used, the slider should also move.

On some Macs, such as the older iMac I had at work, or the Mac mini with an external monitor, selecting "Scaled" reveals a box with resolution options (e.g. 1440 x 900) depending on the display. These resolutions cannot be edited, nor can we add any others. The Brightness slider and the "Automatic" checkbox are included as normal. When some 3rd party displays are used, there may be additional buttons for refresh rate (e.g 60Hz and 75Hz) or for rotation (90°, 180°, etc.)

In his article, "Users Report Loss of HiDPI Scaling on External Displays in macOS Sierra" Tim Hardwick (MacRumors) outlines problems that some users with certain displays have experienced. They are no longer able to access scaled HiDPI resolutions beyond 1920x1080 and (currently) the only way to work with these is to roll back to El Capitan.

Note also, the Rotation button should not be used with a MacBook Pro for the time being as this may cause an unrecoverable problem (I had to recover using Time Machine backup twice while testing this). The Rotation worked fine with a Mac mini and the Dell monitor attached.

To enable the Rotation option on any computer, start System Preferences (if already running, Quit first). Click on the Displays icon while holding the Option + Command keys. The Rotation button should appear. While this may be useful on some external displays, using this on some computers or displays may have unintended consequences. If you are not sure, this should not be used.

Pressing the Option key will show a "Detect Displays" button at bottom right on some Macs. This is used when an external display is connected. In most cases, however, the Display Preferences will detect the display automatically and this will not be necessary. At the bottom left of the panel is a checkbox marked "Show mirroring options in the menu bar when available."

On some computers that are used with the Apple AirPlay feature, for example to link the computer to a TV screen, a button marked AirPlay Display will be available. If no suitable display is attached, this will only show the "Off" option.

Color

There is a warning here: if you are not sure, don't touch.

The default display for the Mac is shown. Below is a checkbox marked, "Show profiles for this display only". When this is unchecked, any profiles previously created are shown in the main window. Highlighting a profile will change the display to the specific settings for that profile. To the right are three buttons: Open Profile, Delete Profile, and Calibrate.

• Open Profile displays a panel in Color Sync Utility (an app in Utilities). The panel shows technical information concerning the specific profile selected in .ICC file format (Color profile format standardized by the International Color Consortium).

• Delete Profile is available for the default Color LCD settings on my MacBook Pro. If Delete is pressed a warning is displayed. Not all other profiles can be deleted, but if the Delete button is pressed a warning appears.

• Calibrate brings up a utility now renamed Display Calibrator (the panel is marked Display Calibrator Assistant). The utility walks users through the process of calibration (should this be needed) and creates a new profile. The computer can always be returned to the original state if required.

[An article on OS X Daily by Paul Horowitz has a good explanation of the calibration process using Display Calibrator.]

Arrangement

Relative to the main display, the second one may be positioned not only to the left or right but also above or below. This may be imagined by moving the cursor to the right edge of the screen (for example) and then seeing it appear on the left side of the second display.

When displays are mirrored, the information on the screen is identical (See also information, below, and Mission Control).

When mirroring is deselected, the Finder menubar is displayed on the main screen of the Mac but not the secondary display.

This feature is especially useful when editing photographs or movies. It is also used with presentations: with Keynote the user's screen can have a Presenter Display which shows current and next slides, along with elapsed times and presenter notes. This is also available in PowerPoint for Macs.

Mission Control has a new option for displays to have separate spaces. This requires the user to logout for this to become available. (see notes below). When this is used, the Finder menubar is shown on displays that are not mirrored: greyed out when the external display is not the main window, but solid white when user clicks on the desktop of that screen. When the external display is the main window, the menubar on the Mac is greyed out.

When two (or more) displays are used, a second panel appears with controls for the extra output that are similar to the main panel. Instead of a Mac there is a display icon that matches the unit connected.

Depending on which of the displays is selected as the optimal choice when Mirroring was on (Mac or external) an "Arrangement" pane will be added. In my case, when the Acer monitor in my office was shown on the "Optimize for" button, that panel had the three panels, while the Mac had the original Display and Color panels.

When mirroring was off, the resolution adjusted itself to the best for the respective display, so while the MacBook Pro was running in its optimum 1440 x 900, the Acer display was at a 1600 x 900 resolution.

When an external display is attached, a button appears at the bottom right of both panels, marked Gather Windows. Panels for Mac and external display brought together. This works in whichever window the panel is when the button is pressed, so if it is in a window on an external display (mirrored or not), pressing the Gather Windows button will move both panels to that external window. In use, the second panel moves to the external source when adjustments are made but may be hidden on that second display, so this feature is useful

By clicking on the white Finder bar at the top of the blue Window shown in the preferences display it can be dragged to another of the windows shown. With this, the window on the external display may become the main (Finder) window (see above).

Comments on Displays in Sierra

I am aware there are some differences with certain monitors and screen capabilities, for example, I have not been able to examine the panel for any special information when 4K displays are used (and certainly have no knowledge of the latest iMac with 5K Retina display). The information in System Preferences > Displays is not always easy to discover, so this is presented as a general look at the panel and its capabilities.

Note also the comments above concerning the changes that may not suit all users, particularly with the lack of scaling options (Tim Hardwick MacRumors) and my own experiences with Rotation on the MacBook Pro I use.

See Also:

• Accessibility (1) - General and Vision
• Accessibility (2) - Media, Hearing and Interacting
• Accessibility (3) - Interacting: Switch Control and Dwell Control
• App Store
• Bluetooth
• CDs & DVDs
• Date & Time
• Desktop & Screensaver
• Mission Control

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand. He wrote in the Bangkok Post, Database supplement on IT subjects. For the last seven years of Database he wrote a column on Apple and Macs. He is now continuing that in the Bangkok Post supplement, Life. He can be followed on Twitter (@extensions_th)