AppleFontSmoothing Has No Effect On My ViewSonic VX2450

A couple things to consider:

• Do you see a difference with the various AppleFontSmoothing settings on your main display?
• Are you seeing this in all apps, or just one or two?
  • Some programs render fonts independently of the OS, so changing the global font smoothing won't make a difference in them
• What is the physical connection between the MacBook and the Viewsonic?
  1. mDP to VGA adapter?
  2. mDP to DVI adapter?
  3. mDP to HDMI adapter?
     • Analog signals on VGA might not support the resolution
     • Make sure any OSD controls for the port you're using have the correct settings
• How have you configured the Viewsonic, relative to your MacBook's main panel?
  1. Mirroring the internal display
     • Select a resolution for your main display that is an even factor of your Viewsonic's native resolution
  2. Set as its own independent display
     • Choose the Viewsonic's native resolution

Hope one of these leads you down a path that ends in a pretty picture.