Here, from Bill Hunt’s review:
Star Wars (now known as A New Hope) was shot on 35 mm photochemical film using Arriflex and Panavision cameras with Panavision C-Series anamorphic lenses, while its analog visual effects were produced in VistaVision. It was finished on film as a cut negative at the 2.39:1 aspect ratio, from which a color-timed master interpositive and dupe negatives were created. For the 1997 Special Edition release, the cut negative was scanned in 2K, new digital VFX were produced at sub-2K resolution, and a new film-out master interpositive element was created. This process was repeated in 2003-2004 by Lowry Digital, with a new 10-bit 2K scan done for the DVD release (complete with more digital VFX tweaks and a color grade supervised by Lucas), resulting in the creation of a 2K Digital Intermediate. This source was used again for the 2011 Blu-ray release, though with a bit more Lowry Digital remastering (and still more new digital VFX and color timing tweaks).
As many of you know, around this time there was a plan to bring all of the films to theaters in 3D—a plan that was posponed and eventually scrapped after the The Phantom Menace 3D release, as Lucas was focused on selling the Star Wars franchise to Disney. In the wake of Disney’s purchase in 2012, a decision was made to protect the studio’s investment by creating new 4K Digital Intermediates of the films and to ensure that all of the photochemical and digital assets were properly cataloged and preserved (a process that continued through 2014). For Star Wars, Empire, and Jedi, all of the original camera neg, the VistaVision effects footage, and SEfilm-outs was scanned in 16-bit 4K by Reliance MediaWorks (formerly Lowry Digital). Lucas once again took the opportunity to tweak the editing, digital VFX, and color timing. In addition to the new 4K DIs, new film-out protection master interpositives were created. New cut negatives were created as well, combining the original camera negative with film-out internegative of the new VFX. (This is why it’s often said that the original theatrical versions technically no longer exist—the OCN has been conformed to the new versions. However, I’ve confirmed with individuals directly responsible that everything—including all theatrical film trims—is well preserved and protected by Disney.) The studio’s new Ultra HD releases (and the recent Disney+ versions) were mastered from these 4K DIs, complete with color grading for high dynamic range (only HDR10 is available on the discs, but Dolby Vision is available on the Digital version).
Disney’s 4K disc presentation obviously includes all the latest tweaks and changes seen in the Disney+ version, but the image quality is superior in every respect. (Note that the 20th Century Fox logo remains intact.) The average datarate is in the 60-70 Mbps range (vs 15-25 Mbps via streaming) and that extra bandwidth makes a huge difference. Detail is clean, apart from the occasional optical softness, with mostly well refined fine detail and texturing. Photochemical grain is extremely light, suggesting a bit of DNR applied. This is also a very restrained high dynamic range grade, which might surprise some people, but it means that the film’s original theatrical appearance is well maintained. Peak brightness is 1000 nits with a deep floor (per the disc’s metadata), so the shadows are inky-black while retaining nice detail. The 10-bit color adds genuinely impressive but subtle nuances to the film’s palette. Skin tones are natural, C-3PO’s gold plating has a rich luster, the sands of the Tatooine desert exhibit a greater variation that you’ll have appreciated before. It appears that some extra “film-look” processing has been done to the 1997 and 2004 Special Edition footage, so that while it’s still obviously of lesser resolution than the live action footage (with more DNR and some edge enhancement baked in), the differences are a bit less glaring than they were on the previous Blu-ray release. This image isn’t perfect, but it’s quite simply the best this film has ever looked in the home.