John Doom said:

I thought composites were done on a dupe? That's probably why they were able to re-composite the effects for the SE in the first place.

Huh? I'm a bit confused by your wording here. You can't recomposite a composite... Much less a duplicate of a composite.

In special effects work, you shoot your individual elements (a TIE fighter is one element, a millenium falcon another, laser blasts another, star fields etc etc) on normal negative film. Then, you run all of those different elements through a special optical printer. So you load up the developed shot of the star field and some low-grain negative stock to reprint the shot onto. You copy the starfield, then rewind the negative. Load in the TIE fighter, copy that on the negative then rewind it again. Load in the millenium falcon, etc. Now all of these elements are copied onto one negative. This is the composite.*

The problem with Star Wars is that they used a highly unstable filmstock to do the original photochemical compositing and these shots are pretty much gone now. The negative that the effects shot elements were shot on should be fine.

For the SE, they took the individual elements and put them back together on a computer using more modern techniques (no matte lines, garbage mattes etc)

*I've obviously simplified the process. For example the effects makers would have needed to create traveling mattes by recopying the blue screen shots on high contrast B/W film several times to get a pure black and white image.