It is in this facility that the original movie negatives from the nearby Warner Bros. vault (in which films are kept at a brisk 45°) go digital. The “4K” refers to the 4,000 lines of resolution at which the movies are scanned – more than triple that of 1080p high-def. And for even more perspective: Your typical theatrical film tops out with a rez of 3K to 4K (few actually reach the 4K level).

via Blade Runner on the Cutting Edge | Sound and Vision Magazine.

def one of the best bluray examples in terms archive restoring and xtras given.. unlike avatar bluray which has nothing(admittedly it does look good already)