Sony has unveiled its new lineup of Xperia smartphones, and this year's headline model is the Xperia Z5 Premium. Available in chrome, black, and gold, the Z5 Premium looks undeniably luxurious, and the company claims its 5.5-inch 4K display is a first for a smartphone. However, with internal specs that are identical to the smaller, more reserved Xperia Z5 (and not far off the "pocket friendly" Z5 Compact), it's not clear if the Premium has more to show beyond a rich, glossy finish.

Like the Z5 and Z5 Compact, the Premium boasts a new fingerprint sensor built into a redesigned power button on the side of the device. (Sony says this location is marginally more convenient than a sensor at the bottom of the phone and I agree — marginally.) There's a Snapdragon 810 64-bit processor and 3GB of RAM powering the device, and the same 23-megapixel camera that Sony's putting into the Z5 and Z5 Compact. The company claims it has the fastest autofocus on the market — just 0.03 seconds — and is making big promises about solving familiar "pain points" for smartphone cameras, like taking pictures in low light. Judgement on that will have to wait for a full review.

Like the Z5 and Z5 Compact, the Premium has a new fingerprint sensor built into the redesigned power button on the side of the device.

The Z5 Premium's screen, however, is more immediately impressive. The 4K resolution of the 5.5-inch display gives an intimidating pixel density of 806 ppi (the resolution of the 5.5-inch iPhone 6 Plus is 401 ppi), and while it's difficult to say for certain whether it's the best screen we've seen on a smartphone, looking at the preprepared 4K footage Sony included for its demo it would be hard to say it doesn't deserve a place on the podium.

What will 4K do to Sony's promise of up to two days' battery life?

This, however, could present problems. Leaving aside the fact that Sony has previously said there's no need for 2K screens on smartphones (the company says the jump to 4K is worthwhile because the difference in quality is far more substantial), 4K smartphones face the same problems as 4K TVs: a dearth of compatible footage. Sony promises that the Z5 Premium will upscale videos and images to 4K, but upscaling is usually not as good as the real thing. (We didn't get a chance to try out Sony's method.) There's also the issue of battery. Although Sony promises that the Z5 Premium will last up to two days on a single charge just like the Z5 and Z5 Compact, it's not clear how this figure will hold up to any sustained video use on a 4K display. The Z5 Premium does come with a hearty 3,430mAh battery (a shade less than the long-lasting Moto X Play and its 3,630mAh capacity ), but 4K will still take its toll.

These questions aside, however, it's easy to say that the Premium is beautiful. The chrome, black, and gold variations are all glossy and rich-looking, with a liquid finish to them like newly poured ingots. They're heavy, yes — 180 grams compared to the iPhone 6 Plus' 172 gram weight — but the design quality means they feel reassuringly solid, rather than a burden. That being said, we wonder how it would feel carrying one around in our pockets day after day after day, and this seems like it might be the biggest issue for the Z5 Premium. With its luxurious appearance and vivid screen it looks fantastic on a stand, but the shine might wear off with some day to day use.