Saw the 12-perf IMAX film version. Really gripping, especially when the fighter planes bank and turn. Really visceral stuff with the IMAX close-ups during the ship sinking, and the derelict boat being assaulted with rifle fire. Undoubtedly much more of an experience than a mere Panavision film or full-digital production would have been.
The only thing that stood out as off-key or fake on the IMAX print was a shot of Tom Hardy's Spitfire as he cruises along the beach before landing. IMAX, in addition to powering the close-quarters oomph and the aerial grandeur, also makes it crystal clear that a CGI strip of Dunkirk town has been overlaid atop the beach and around the top of the plane. Small price to pay for a well-realized group of high-visual-resolution setpieces.
On the 4K video, the matted-over CGI was unnoticeable. The beach fly-by looked totally natural. I guess home video has a way to go to equal IMAX 12-perf.
Or it could be that the CGI was cleaned up for the home video release. Or a matter calibration on the video display. Home video can have different gamma or PQ (Perceptual Quotient) settings than what you will see from projected film or digital in a commercial cinema. Since this determines the rise out of black or even how the different tones are mapped, sometimes how these parameters are set can reveal or hide various flaws or issues in the picture. I'm finding on the home cinema side calibrators are still struggling with how to properly calibrate UHD projectors and displays.
FWIW it's extremely rare to find any true 4K DCPs playing in digital cinemas. I imagine that a true 4K DCP could outperform even the best physically projected IMAX footage (as evidenced by the comparative shootout I linked to previously),
