The Xperia 1 has the latest Qualcomm Snapdragon 855 processor, along with 6GB of RAM and 128GB of storage. It's clad in a waterproof body and boasts a 3,300 mAh battery, which may not be quite enough for what's likely to be a power-hungry phone. Unfortunately, the fingerprint reader is mounted on the side, not on the screen like recent devices.
The Xperia 1 has a triple-camera with three different focal lengths: 16mm for wide shots, a 26mm normal view, and a 52mm lens for telephoto shooting (all 35mm equivalent). With a 12-megapixel sensor, it lacks the resolution of recent 40-megapixel smartphone cameras. However, it makes up for that in low-light handling, thanks to the large 1.4μm dual photo diode image sensor and RAW noise reduction. It inherits the eye autofocus (Eye AF) tracking from its mirrorless A7 cameras, and delivers 10 fps shooting speeds with autofocus and auto-exposure enabled.
As for movie shooting, Sony collaborated with the engineers from its professional digital cinema camera division CineAlta. You can shoot 4K HDR at 24 fps in a 21:9 widescreen cinetmatic format. To help get rid of camera shake, Sony has created a hybrid stabilization system that uses its optical SteadyShot tech. You also get eight cinematic color presets to create different moods.
4K smartphone screens have been pretty rare, with Sony one of the few to do it before with the Xperia X5 Premium in 2015 and more recently, the Xperia XZ Premium. However, the latest model has an OLED, rather than an LCD screen like the previous models. It's also "inspired by master monitor color reproduction from Sony's professional technology, which is used in leading Hollywood studio productions," Sony said. That means you get 10-bit (1 billion) colors, as well as support for the professional ITU-R BT.2020 color space. In other words, you'll be able to watch movies exactly as they were meant to be seen.
However, it's next to impossible to find 21:9 content on sites like YouTube, so you'll most likely get black side bars most of the time and resolution below 4K. The Xperia 1 has no notch, just a regular bezel on top for the front camera. Given the large size and aspect ratio of the phone, that makes it incredibly tall compared to notched models like Samsung's S10+ and the iPhone XS Max.
Other features include Dolby Atmos sound and a "game enhancer" that blocks notifications and other distractions during gaming and more. The 21:9 display will also make for a deeper unrestricted field of view, Sony notes, and it's working with partners on games like Fortnite to support it.
In sum, Sony finally seems to be putting the muscle from its gaming, camera, and movie studio brands into its mobile devices, making the Xperia 1 a very high-tech flagship. Whether that will translate into better sales remains to be seen, but it'll arrive in the US in late Spring 2019. Sony has yet to name a price, but given the level of tech, set your expectations accordingly.
Update 2/25/19: Updated to note that Sony also built the 4K HDR Xperia XZ Premium (thanks, Evan).