Sony has published an extensive interview with the designers of its Xperia phones and it has some interesting tidbits. The designers are concerned with not just the evolution of smartphone design, but also with change. They see that smartphone design is getting stale and are keen to keep the Xperia phones fresh.
The Sony Xperia XZ2 Premium is the model that lives on the cutting edge. It introduced HDR video recording to match the 4K HDR capabilities of its screen. Interestingly, the original XZ Premium also had an image sensor capable of HDR video capture, but the chipset couldnt handle it.
Besides balancing improvement with innovation, the Sony team divides features into quality and fun & creative. The 4K HDR video goes into the quality category while things like 960 fps slow-mo and the 3D creator are fun.
The company has been looking into dual camera designs, but until now it focused on single-camera shooters with a focus on a large sensor (1/2.3) and improving the BIONZ image processor. The XZ2 Premium is the first Xperia with the Motion Eye Dual camera, which features two 1/2.3 sensors (one color, one B&W). And it has an increased maximum ISO of 51,200 for shooting fast-moving subjects in the dark.
Going back to screens, the choice between the standard 16:9 and the new taller aspect ratios comes down to the size of the screen and the primary use for the phone. Sony believes 18:9 screens make phones better communication tools while 16:9 is best for multimedia.
As for the other recent trend bezel-less phones Sony is conservative because it wants to deliver a phone with good ergonomics. Its not just that, making the bezels too thin will interfere with the camera, speakers and other hardware.
But Sony is working on making the bezels of its Xperia phones thinner the side bezels mostly, but also the vertical ones.
Source (in Japanese)