Episode I is not digital.
He had just done AOTC and was working on ROTS when the 2004 masters were done. He was already in all-digital mode, and I am certain he wanted the OT DVDS to aesthetically match up with what he was making at the time.
And he failed miserably each and every time. The only prequel that actually looks somewhat like an original Star Wars film is The Phantom Menace