You_Too said:

Interesting. And it's also weird how bright all shots are. Even ANH looks much less crushed in the shadow detail.

I found one shot with a lot of compression artefacts though: http://ninfo.eu/wp-content/gallery/StarWars/Episode.4/StarWars.Episode.4.39.jpg

So all of them can't be from a digital intermediate.

Maybe some kind of pre-release promo discs?

Perhaps. I'm pretty sure that TPM and AOTC are from slightly unedited digital intermediates though, there are definately screencaps from both those films that don't fit any releases. Seems only the Prequel Trilogy screencaps are taken from HQ digital intermediates, which would make sense because they are so recent and the last two were shot digitally.

Those Star Wars shots just look like they were taken straight of the 2004 lowry masters (they have the same fake looking frozen grain) that are brightened and have reduced contrast relative to the blu-rays, nothing special there IMO. I'm pretty sure the blu-rays have all that shadow detail as well if you brighten them and reduce contrast. The blu-ray releases look exactly the same image quality wise. I would love to see LF in future do a proper 2k or even 4k master of the star wars original trilogy, I think it would add a lovely 'filmic' feel to these films from all the natural film grain that would appear.