Carl has a 2012 MacBook Pro Retina, and now when he connects it to his Vizio, he's noticed that the screen isn't as clear. The fonts are fuzzy and the image quality varies from app to app. Leo says that it could be that the native resolution of his Vizio screen may not be one that his MacBook understands and therefore, it runs the default resolution, which is generally half the native resolution of the screen. He'll need to figure out what the native resolution of the screen is, divide it by two and choose the best option based on that. Could updating to El Capitan also be a factor? Leo says probably not.
Scooter X says that running the app SwitchResX will help him determine which resolution is optimal for his monitor.