The clip, which can be in its entirely on Zack Snyder’s Vero page, is the opening of the “Knightmare” sequence, which shows Ben Affleck’s Batman coming outside into an apocalypse. The world has been utterly destroyed and has become a wasteland. The remaster work that’s being done is to restore the film’s IMAX presentation, and as you can see in the side by side comparison below, the new version has the camera pulled back, in order to allow for IMAX’s more vertical presentation, but as a result, much more of the frame is actually visible.