If I have learned anything in my many years of Star Wars fandom, it is that George Lucas is a perpetual tinkerer. In many ways he is like Han Solo, constantly working on the Falcon, some times the changes are for the better, and sometimes the changes blow up in his face and end up with a Wookiee or Fanboy shouting at him.
StarWars.com has a nice article about some of the fixes that have been made to the films and the process by which was used to pour over the films in preparation for the Blu-ray release.
The older films of Episode IV, V and VI required special care and attention. Already, for the 2004 release, the movies underwent significant digital restoration to have them align with George Lucas' vision of the six Star Wars movies being a single, seamless presentation. However, that is not to say that that work done for the 2004 release was simply ported over to Blu-ray.
"It went through three phases of QC (quality control) processes," describes Diane Caliva, Production Manager for Media Operations at ILM. "In addition to Lucasfilm reviewing, there were outside companies hired as well. The first was Blu-focus/THX QCing our masters. Then it went through Deluxe and their QC process. And at last was the emulation phase, by the Deluxe team . We would get 'kickback notes', and then Dorne and our team we would assess the shots, and go in and clean up the files."
In addition to some general cosmetic fixes such as correcting colors, fixing digital animation errors, etc. George Lucas will be making a change on the scale of digitally erasing Sebastian Shaw and inserting Hayden Christensen into Return of the Jedi.
As has been long speculated we will be getting a digital Yoda to replace the less then ideal puppet Yoda in Episode I.
MildConcernTV has a nice side by side video comparison of the dueling Yodas.
I generally appreciate the visual and auditory clean ups that have been done to the films, but one thing is for sure....Han Shot First!
SOURCE: Starwars.com and Film School Rejects