My rMBP screen resolution is set to "Best for Retina display". If I "quick view" an image with resolution 1024*1024, the system will display it in a window with 1/4 of the size if I display the same image on a cMBP. I can understand this because I know my screen is retina. However, if I play a 720p video in 100% mode using iTunes, the size of the video screen will be the same as in cMBP, which I don't understand. Both "quick view" and iTunes support retina display, but why I don't get "smaller" "native" 720p display in iTunes?