The Z5 Premium has a 5.5-inch display, with a pixel count of 3,840x2,160 -- the same as a 4K TV. That gives the phone a whopping count of 806 pixels-per-inch, and on top of that Sony says it will upscale your photos and videos to a 4K resolution.
There's no denying that the Premium's display is pin-sharp, with individual pixels impossible to distinguish. That said, smartphone screens with 1080p resolutions are already very impressive, and we can't say we noticed much visible difference between the Z5 Premium and high-res smartphones with dramatically fewer pixels.
You get 32GB of onboard storage, and the expandable memory will support up to 200GB on a microSD card. That's handy if you do manage to find some 4K video to watch on your phone, as ultra-HD video files take up a lot of space.