You must prevent your screen saver from launching during calibration and interfering with measurement.

1. Choose Apple > System Preferences (Mac OS 12), or Apple > System Settings (macOS 13 and up).

2. macOS 12

   1. Click Desktop & Screen Saver.

   2. Click the Screen Saver tab.

   3. Select a screen saver.

   4. Under Start after, set to 30 minutes or longer.

   5. Close the Desktop & Screen Saver window.

3. macOS 13 and up
   1. Go to Apple > System Settings > Screen Saver.
   2. Select a screen saver.
   3. Go to Apple > System Settings > Lock Screen.
   4. Change the drop-down in Start Screen Saver when inactive to 30 minutes or longer.