After updating OS X your primary or secondary monitor no longer fills the screen, but is scaled down to the middle and the display preferences no longer lists vertical resolutions.
After updating some additional options are sometimes reset.
- Go to the System Preferences pane (Apple Icon top left > ‘System Preferences…’)
- Select ‘Displays’
- Holding the option key, click the ‘Scaled’ selection
- After clicking you can now select a vertical size (in this example 1024 x 1280, the larger number should be on the right)