doubleofive said:
Comment on the Blu-ray fixes pointed out there's an extra lightsaber glow above Luke in the GOUT. This is a 1997 change.
Similar lightsaber FX-artifacting can be seen in TESB at the end of reel 5. (In the shot where Vader is forced off the ledge in the carbon freeze chamber.)
One close-up shot of Vader in the first film during the duel contains a repeated frame when we cut to him in the original film. When they went back to the negative to replace the original lightsaber effects for the dreaded 2004 DVD version they also took the opportunity to restore the missing footage. As this is one single frame we're talking about, I guess there is a possibility that the frame could have been "restored" by digital manipulation if the footage was gone for some reason.
2006 Bonus Feature (#127754 & 127755)
The corresponding frames in the DVD version... Top: Not in the original film Below: Used twice
Not necessarily related but a black line at the top of both frames can be seen in the JSC LD transfer which is much more open in its framing compared to the bonus feature.
I noticed that your comparison lack the tweaked ignition of Ben's lighsaber (they tried to make it a bit more smooth by making him ignite it a few frames prior to the original films jump cut).