How does the 4K display work in Xperia 1 or Xperia 1 II?

Xperia 1 and Xperia 1 II display resolution

The Xperia 1 and Xperia 1 II conforms to the Sony 4K definition of 3,840 horizontal pixels (in landscape orientation). With a 21:9 aspect ratio, this results in 3,840 x 1,644 pixel resolution.

Watching 4K video in 21:9 aspect ratio

The Xperia 1 and Xperia 1 II lets you enjoy 21:9 aspect ratio content, edge to edge and without letterboxing. This is optimal for movies created in 21:9 format and available in 4K resolution. 

Playing back recorded 4K video in 21:9 aspect ratio

You can record 21:9 4K video using Cinema Pro, and play it back in true 4K quality on the Xperia 1 and Xperia 1 II.

4K is activated in 4K movie playback on YouTube, Cinema Pro, etc. 4K playback depends on apps specification.

Watching non-4K content

Xperia 1 and Xperia 1 II uses advanced upscaling technology to display non-4K content, enhancing contrast, colour and clarity.

Watching content in 16:9 aspect ratio

On the Xperia 1 and Xperia 1 II, content with a 16:9 aspect ratio is by default displayed with pillar boxing. You can also zoom in to fill the screen, with top and bottom cropping as a result.