Some discs were released as "4K Mastered" meaning that the film as mastered in 4K but the resolution is the same as a normal Bluray. Theoretically these releases will have better picture quality than a Bluray NOT mastered in 4k. Be aware though that these are NOT actually UltraHD 4K discs. Those discs will be released starting in 2016. These "4K Mastered" releases are essentially the Bluray version of the "Superbit" DVDs. Also note that not all discs mastered in 4K are prominently marketed as such. Only those discs that have a separate "Mastered in 4K" are indexed separately.
