4K resolution
As noted above, DCI 4K is 40962160, while 4K UHD is 38402160, producing a slight difference in aspect ratio rather than a significant difference in resolution. Traditional displays, such as LCD or OLED, are 3840 pixels across the screen, with each pixel being 1/3840th of the screen width. They do not overlap—if they did, they would suffer reduced detail. The diameter of each pixel is basically 1/3840th of the screen width or 1/2160th of the screen height - either gives the same size pixel. That 38402160 works out to 8.3 megapixels, the official resolution of 4K UHD (and therefore Blu-ray UHD discs).
8K resolution
In 2007, the original 65 mm negative of the 1992 film "Baraka" was re-scanned at 8K with a film scanner built specifically for the job at FotoKem Laboratories, and used to remaster the 2008 Blu-ray release. "Chicago Sun-Times" critic Roger Ebert described the Blu-ray release as "the finest video disc I have ever viewed or ever imagined." A similar 8K scan/4K intermediate digital restoration of "Lawrence of Arabia" was made for Blu-ray and theatrical re-release during 2012 by Sony Pictures to celebrate the film's 50th anniversary. According to Grover Crisp, executive VP of restoration at Sony Pictures, the new 8K scan has such high resolution that when examined, showed a series of fine concentric lines in a pattern "reminiscent of a fingerprint" near the top of the frame. This was caused by the film emulsion melting and cracking in the desert heat during production. Sony had to hire a third party to minimise or eliminate the rippling artifacts in the new restored version.