Brooks said:

What resolution were the scans used for the official blurays? I don't know much about motion film, I've been scanning my still photo negatives at 4800 dpi and that works out to about 100mb a frame too. I would love to see a frame of motion film scanned at 4k (or 10k, wow!).

http://secrethistoryofstarwars.com/savingstarwars.html

This article explains the official restoration process ver well. It's interesting how the first special edition used 2k scans but the DVD/Blu-ray is a 1080p scan