Thanks for weighing in with real-world experience doing film scans.

> From my experience, 4K was the absolute edge you could pull from the best 35mm films... I managed to pull 8K from some 70mm ride footage.

This matches the expert opinion I've heard elsewhere, as well as what was done when scanning Blade Runner (an historically important film now in the national archives). They scanned the 35mm camera negatives at 4K and the 65mm VFX camera negatives at 8k. I'd add that in film scanning, extended color depth is also very important to capturing the full fidelity of what's on the celluloid. An adjacent high-impact factor is how the grain structure of film is handled in post-scan processing. This entails artfully balancing a tricky set of trade-offs because the highest-frequency edge and chroma details are down in the noise floor. Extracting more signal is a knife-edge balance between amplifying noise on one side or suppressing filmic texture on the other. Ultimately, these choices move beyond technical correctness to aesthetic judgement, which I imagine has to be the sweat-inducing part of the job. Anyone really interested in resolution, film scanning and digital cinema should see this in-depth comparison shot by an expert ASC cinematographer specifically to be a definitive set of proofs for the industry. He compares (and pixel-peeps) identical shots from a range of top digital cinema cameras (Arri Alexa, RED, etc) with a high-quality 6K film scan. https://www.yedlin.net/ResDemo/ResDemoPt2.html. I found the results pretty surprising.

> Wizard of Oz is 3x35mm for the color scenes, though. So, in theory you could use some clever algorithm to almost certainly create 8K transfers from it by using the tiny differences between the three frames.

Yes, I really hope that whoever handled the source preparation contributes a technical paper or note on what they did and learned in the process. What I've found so far is far too vague technically but implies they started with the 3-strip camera negatives (perhaps from an earlier scan). As you mentioned, that would enable interesting possibilities for noise reduction by leveraging the differences between the three strips. I kind of hope that sort of noise reduction was actually done by film preservationists in an earlier scan (perhaps for a Blue-ray or UHD release) as the archival source scans deserve the highest fidelity.

As I said in my other, longer post in this thread, I really hope that this effort for a Sphere version will also yield a less extreme 2.39:1 (Cinema Scope), 2.74:1 (Super Panavision) or even IMAX version from the 4:3 aspect original. I appreciate and value wide format cinema but personally think the Sphere FOV is so incredibly extreme it has more negatives than positives for cinematic storytelling. FOVs as extreme as Sphere are really only suitable for theme park attractions, amusement park rides or head-mounted immersive stereo 3D. I realize that the opportunity to collect $100 a ticket at the Sphere was too good for Warner to pass up but we're talking about a cinematic film that's become a cultural artifact. I'm not so purist as to balk at the idea of extending such a classic film with VFX and AI assist but a more "serious" cinematic version would be wonderful in addition to the over-the-top Sphere format. Hopefully, the Sphere version is a limited time release window and there's a subsequent IMAX release (15 perf / 70mm please) and an eventual 2.4:1 UHD (which I'd definitely buy).