Na toll - danke, Apple! Hier schwarz auf weiß
https://support.apple.com/en-us/HT203799
OS X Mavericks: Using brightness controls with vintage and obsolete displays
You may notice when using older Apple displays with Mavericks that you cannot adjust your display's brightness using its built-in controls. Additionally, the Brightness slider may no longer appear in the Displays pane of System Preferences.
The following vintage and obsolete displays are not supported with OS X Mavericks v10.9 or later:
Apple Studio Display 15-inch ADC
Apple Studio Display 17-inch ADC
Apple Cinema Display 20-inch ADC
Apple Cinema Display 22-inch ADC
Apple Cinema Display 23-inch ADC
Apple Studio Display 15-inch DVI
Apple Cinema Display (Original) DVI
These displays were designed to work with older hardware that is incompatible with OS X Mavericks. To avoid incompatibility issues, use a newer display that includes a DVI, VGA, HDMI, Mini DisplayPort, or Thunderbolt connector with Mavericks.
OS X Mavericks: Using brightness controls with vintage and obsolete displays
You may notice when using older Apple displays with Mavericks that you cannot adjust your display's brightness using its built-in controls. Additionally, the Brightness slider may no longer appear in the Displays pane of System Preferences.
The following vintage and obsolete displays are not supported with OS X Mavericks v10.9 or later:
Apple Studio Display 15-inch ADC
Apple Studio Display 17-inch ADC
Apple Cinema Display 20-inch ADC
Apple Cinema Display 22-inch ADC
Apple Cinema Display 23-inch ADC
Apple Studio Display 15-inch DVI
Apple Cinema Display (Original) DVI
These displays were designed to work with older hardware that is incompatible with OS X Mavericks. To avoid incompatibility issues, use a newer display that includes a DVI, VGA, HDMI, Mini DisplayPort, or Thunderbolt connector with Mavericks.