AMITIAE - Friday 24 October 2014

System Preferences in OS X 10.10, Yosemite: Displays

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By Graham K. Rogers

In System Preferences the Displays Preferences panel appears similar to that in the last version of OS X, although panels differ depending on the computer. One important feature concerning Spaces and presentations is affected by Mission Control preferences.

The Displays panel controls the way screens show their content. It is normally in two sections: Display and Color. For a computer with an inbuilt display, like the MacBook Pro or the iMac, the information will be for the machine's own monitor. This will differ for computers that use an external device (Mac Pro, Mac mini). An additional panel - Arrangement - will appear when extra external displays are connected.


The Display pane appears similar to that in previous versions of OS X. As before, icons for the specific displays being controlled (internal or external) are used. On my computer, for example, the icon for the Retina display panel clearly shows a MacBook Pro, right down to the "MacBook Pro" characters, the black screen surround, the infrared detector and the iSight camera (you have to look hard).

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

There are two Resolution options shown on the right: Best for display and Scaled. The resolutions will appear when Scaled is selected or when an external monitor is attached. With OS X 10.9, Mavericks 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. A text describing the approximate resolution appears beneath the image. Selecting a new setting changes the Mac icon.

"Best for display" is for users who will want to leave well alone and will be 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 moves as well.

On some Macs, such as the iMac I use at work, selecting "Scaled" reveals a box now with 4 options, from 1024 x 640 up to the optimal 1440 x 900. These resolutions cannot be edited, nor can we add any others. Below is the Brightness slider and the "Automatic" checkbox.

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, although in most cases, the Display Preferences will detect the display automatically. At the bottom left of the panel is a checkbox marked "Show mirroring options in the menu bar when available."


The pane marked Color is to show and, if necessary, add or change any color profiles by way of calibration. Most home users will not need this, but for imaging professionals this ability to calibrate displays is critical. While professional photographers or print houses may need to check calibration regularly, they will have specialist knowledge and equipment to assist with this.

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 not available for the default Color LCD settings on my MacBook Pro. Other profiles can be deleted.

  • Calibrate brings up a utility now renamed Display Calibrator (the panel is marked Display Calibrator Assistant). This also has an "Expert mode" accessed by checking a box. 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.

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


With Macs it has always been possible to set up the way an external monitor displays information, either by mirroring the main display (a clone) or a side-by-side setup. I normally use this for presentation of information in a classroom, using an overhead projector.

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 (image above) 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).

Displays On the external display panel on my computer, when mirroring is OFF, I also have a Rotation button. I added this some time back using a Terminal command in the main panel (see below), but it is now only shown when a suitable external monitor is attached.

With this, I am able to turn the display through 90, 180 and 270 degree options which may be useful when certain displays are used or some images need to be shown at different angles.

Comments on Displays in Yosemite

Those having problems making presentations display correctly using the Mac and external monitors may also want to look at Mission Control where a checkbox, marked "Displays have separate Spaces" will affect the way presentations and (particularly) presenter displays are shown. When the box is unchecked, using displays that were not mirrored, the presenter display was on the MacBook Pro with the slides displayed on the external display (as in previous versions of OS X).

I have provided as much information as I can, but 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.

See Also:

Graham K. Rogers teaches at the Faculty of Engineering, Mahidol University in Thailand where he is also Assistant Dean. 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.



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