The 4K and Blu-ray will be 4:3
The film was shot on IMAX cameras 35mm with 1.33:1 aspect ratio
Zack Snyder’s intent was to have the movie, the entire film, play in a gigantic 1:43 aspect ratio on a giant IMAX screen,
The ratio 1.33:1 is the same as the 4:3 ratio of a television screen.
To see the film in 1.78:1 or 1.85:1 aspect ratio that means cropping the upper and bottom portions of the image for regular movie theaters to shown in widescreen that's what they did for the cinema release in 2017 and for home media releases
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You see more image with the 4:3 aspect ratio as it means the image does not need to be cropped
Zack Snyder’s want's you to watch the film in it's original aspect ratio without been cropped for widescreen