Sony Xperia Z5 Premium review

Of all the companies you'd expect to be the first to release a 4K smartphone, Sony would struggle to make the shortlist; as Samsung, LG and Motorola all moved up to 2,560x1,440, Sony stubbornly stuck with 1080p for the Xperia Z5. Despite that, here we are - the world's first smartphone with a 4K display is actually a Sony. The Xperia Z5 Premium overtakes its sibling as the best Sony has to offer going in to 2016, but this monster phablet arguably has more in common with the ill-fated Xperia Z3+ than the rest of the Z5 range.

Part of this is down to the design, which shuns Sony's gorgeous frosted glass for a glossy, almost mirror-like finish on the back. In fact, the chrome model I saw at Sony's launch event was so reflective that you could easily use it to fix your hair or do your morning make-up on the train. The effect is more subtle on the other colour choices, but it makes little difference when none are as easy to grip as the standard Z5. It's also a complete fingerprint magnet, rather detracting from its premium status, despite the classy engraved Xperia logo on the side.

^ The Chrome version of the Z5 Premium has a full mirror finish, but the gold and black models aren't quite so reflective

It does, however, use the same flush fingerprint sensor as the rest of the Z5 family. It's a shame Sony had to get rid of its round, machined-finish power button in the process, as the fingerprint sensor doesn't provide nearly as much tactile feedback when you press it down to turn the screen on to unlock the phone, but it is one of the best-placed fingerprint sensors I've seen so far. It's also very quick, taking little more than a second to unlock it once you've pressed the power button.

4K Display

Of course, the main attraction is that 3,840x2,160 resolution display, which across 5.5in gives the Z5 Premium an insanely high pixel density of 806 pixels-per-inch. That's more than twice as sharp as the iPhone 6S Plus and 1.5x as sharp as the LG G4, both of which have 5.5in, but only resolutions of 1,920x1,080 and 2,560x1,440 respectively.

Except, the whole thing is a bit of a misnomer, as most of the time it's not rendering in 4K at all. Instead, it uses a standard 1,920x1,080 resolution for everything outside of Sony's Album and Movie apps. The home screen, third-party apps and web browsers are all rendered at 1080p. Android 5.1.1 simply doesn't support 4K, with Marshmallow expected to add UHD compatibility officially in an update. According to Sony, the only time the Z5 Premium actually does render in 4K,is when you're viewing 4K content you've captured using the device, or third-party 4K content from streaming services.

The latter isn't even strictly true at the moment either, as third party apps such as Netflix and YouTube don't support 4K resolutions, so the only conceivable way you'll actually be using all those pixels right now is for watching 4K video or looking at 4K photos you've shot using the phone's camera. You can see the difference compared to 1080p video, but you do have to hold the phone rather close to your face to appreciate it. View it from a normal viewing distance, and the crisp detail becomes significantly harder to pick out. It's hardly the most compelling reason to shell out either £600 SIM-free or £49-per-month on contract, but Sony hopes it will at least provide a bit of future-proofing in the device for when app developers (and Android) eventually catch up.

Battery Life

Sony's chief reason for rendering at 1,080p is to help preserve the phone's battery life, as, understandably, rendering at 4K all the time would tear through the 3,430mAh battery in no time at all. It doesn't seem to have done a particularly great job, though, as the Z5 Premium lasted a pitiful 9h 38m in our continuous video playback test. This is the worst result I've seen across the Z5 family, with the Z5 lasting 11h 29m and the Z5 Compact managing an even more impressive 13h 21m. It's also pretty poor compared to other phablets, as other handsets with batteries of this size have all lasted well into double figures.

Image quality

Display quality doesn't quite measure up to the normal Z5 either. While its 97.6% coverage of the sRGB colour gamut means it still has one of the best IPS displays around, its accuracy levels are just a fraction below the Z5's. When I compared them side-by-side for example, the Z5 Premium had a noticeably cooler overall colour temperature compared to the Z5, which meant that warmer colours didn't look quite as rich or punchy.

The Z5 Premium's screen also isn't as bright as the Z5's, as I only measured a peak brightness level of 455.25cd/m2 compared to the Z5's massive 684.25cd/m2. As a result, whites also weren't nearly as clean and pure on the Z5 Premium as they were on its little brother, which also had a knock-on effect on its overall colour vibrancy. It's not all bad news, though, as the Z5 Premium's contrast ratio of 1,255:1 and black level of 0.36cd/m2 beats both of its smaller siblings, leading to deeper blacks and more detailed images.

Performance

Aside from the display, there's very little else to distinguish the Z5 Premium from Sony's other two flagships, as they all use the same octa-core, 2.0GHz Qualcomm Snapdragon 810 chip and the same 23-megapixel camera. Admittedly, the Z5 Premium proved a little faster in our benchmark scores, with a score of 1,349 in the Geekbench 3 single core test putting it around 100 points ahead of the Xperia Z5. A multicore score of 4,667 is more than 600 points in front, making it even faster than the Galaxy S6.

In practice, though, it took the Z5 Premium just as long to loads apps as the Z5. It's still pretty quick, but does little to help justify the Z5 Premium's higher price. Web browsing performance was also pretty equal. With a score of 1,524 in Peacekeeper, the Z5 Premium coped beautifully with complex web pages, and didn't even stutter when it was faced with images, embedded videos and adverts within a single article.

Likewise, graphics performance was nigh on identical; 1,565 frames in GFX Bench GL's offscreen Manhattan test produced a highly respectable average of 25fps, the same as the Z5 Compact and just one frame behind the Z5. With this much power behind it, games such as Hearthstone proved no problem at all for the Z5 Premium, and simpler titles like Threes ran beautifully.

Camera

There was little to separate the Z5 Premium's camera from the vanilla Z5's. Images were well-exposed in our outdoor test shots, and colours and contrast levels were excellent, but look closer and there are almost identical levels of post-processing noise and grain. Objects in the centre of the frame were reasonably sharp, but further out it became noticeably fuzzier, with small details becoming all but lost in the haze. Switching to Manual mode and enabling HDR didn't help matters either.

^ The camera was a little disappointing outdoors, as there was a lot of post-processing noise present at full resolution, particularly toward the edge of the frame

Thankfully, indoor performance was significantly better. Textures in our still life arrangement were still a little blurred in low light, but grain was kept to a minimum across the frame and colours looked pleasingly neutral. There was also an excellent level of contrast on show, and the flash kept images nice and clean.

^ In low light, textures were a little hazy, but overall there wasn't as much grain as our outdoor shots

^ With our external lamp turned on, the Xperia Z5 Premium produced excellent indoor shots, showing plenty of detail and crisp, neutral colours

Conclusion

Ultimately, though, the Z5 Premium just doesn't do enough to justify choosing this over the original Z5. A 4K display is great in theory but disappointing in practice due to Android's limitations, not to mention a massive battery drain even when rendering at 1080p. The camera and overall performance don't offer any significant gains over the standard Z5, either. It's still one of the quickest Android phones around, but when the Z5 does exactly the same for £15-per-month or £80 less SIM-free, there's simply no contest. The 4K display may come into its own once Sony rolls out its Android Marshmallow update, but right now the Z5 Premium feels like a very expensive, and rather meaningless, experiment.