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Does the Sony Xperia Z5 Premium need a 4K screen? Advantages and disadvantages

Sony just launched the Xperia Z5 Premium, a 5.5-inch mobile boasting the world’s first 4K smartphone screen. But will that really mean better visuals compared with Quad HD screens found on other phones such as the LG G4 and Galaxy S6? And what are the drawbacks?

If someone says 4K, you probably think of tellies that cost as much as your gross annual salary. Boasting an impressive 8 million pixels (four times the number found on ‘bog-standard’ Full HD displays), 4K panels produce ridiculously sharp visuals. You can find some top-end PC monitors packing a 4K resolution these days, but it’s still a very expensive technology confined to the homes of the well-off.

There’s been talk of smartphones packing a 4K resolution for a while now, with Samsung’s Galaxy Note 5 expected to be the first to the plate. But Sony is the first to make mobile history with its new Xperia Z5 Premium handset, which sports the rather mind-bending 3840×2160 pixel resolution usually reserved for massive TVs.

So, when you take that many pixels and compress them into such a small display, can you actually notice any real difference over the current industry standards of Full HD (1920×1080) and Quad HD (2560×1440)?

Back when Apple revealed its first Retina screen, the Cupertino company claimed that its 326 pixels-per-inch was as good as we’d ever need on a mobile screen. Of course, back then phone screens were only around 4 inches. Nowadays they’re almost always 5-inches and larger, so flagship phones come packing a minimum Full HD resolution. For instance, Sony’s Xperia Z5 flagship has a Full HD 5.2-inch screen, which crams in 428 pixels-per-inch.

Full HD panels are perfectly sharp on a miniature device. You’d have to squint incredibly hard to make out individual pixels and high-def movies look nice and crisp. However, there is a clear difference between Full HD and Quad HD, with the likes of Samsung’s Galaxy S6 smartphone boasting incredibly sharp visuals. Perhaps most people wouldn’t notice the difference until the screens were shown side-by-side, and almost no one would miss the intense clarity of Quad HD if they had to drop back to a Full HD mobile. But at least you can see the improvement.

However, most experts in vision tech agree that the cut-off point where humans can no longer notice any difference is around 500 to 600 pixels-per-inch. So, with a mighty 806 pixels-per-inch the Xperia Z5 Premium appears to be a step too far – if the experts have it right.

Then there’s the question of content. So far there’s a limited selection of 4K video on YouTube, while the likes of Sony’s flagship phones and the latest action cams allow you to shoot 4K footage, but there really isn’t much support for these super-crazy-def screens right now.

Maybe in a year or two that’ll change, but if you had a solid selection of online 4K content to choose from, would you even be able to stream it? You’d need a recommended 20Mbps connection in order to watch video at that resolution, which is beyond what we clock on our 4G phones most days. And not too many people can boast broadband that fast just yet either.

Sony’s solution to the problem of no 4K content is to upscale HD video from existing sources like Netflix, to fit the higher resolution. We’ve yet to see this in action, but if it actually works, that would be a neat little trick that eliminates the previous two problems. But that still leaves one more burning issue: the impact on performance and battery life.

More pixels means more processing power is needed to run the screen, which in turn could slow down the phone or cause it to overheat. Bearing in mind that the Snapdragon 810 processor powers the Xperia Z5 Premium – the same chipset found on the too-hot-to-handle Xperia Z3+ – we’re a little worried that temperature might be a serious issue during video marathons. We’ll be sure to do plenty of testing for our full review.

And of course, battery life could be seriously impacted by a higher-res panel, but so far phones have stood up to the pressures of Quad HD without issue; the LG G4 gives us a day and a half of life with everyday use. And Sony reckons that its new smart processing algorithms will help the Xperia Z5 Premium’s 3,430mAh battery to last a full two days. We reckon that’s a tad optimistic, but if we can still get over a day with plenty of screen-on time, we’ll count that as a victory.

Of course, one of the most compelling reasons for a 4K screen on a smartphone is the VR potential. Samsung’s Gear VR proved that it’s actually a pretty good idea to use a phone as a VR headset display, but also that a Full HD screen isn’t high res enough to produce sharp visuals when the panel is that close to your mug.

A 4K smartphone screen would solve that problem outright, but Sony’s own VR tech, Project Morpheus, has a built-in Full HD screen. So unless Sony (or a third party company) comes up with a Gear VR-style chassis for the Xperia Z5 Premium to rest in, this could be a massive missed opportunity.

Check back soon for our full Xperia Z5 Premium review, and in the meantime check out our hands-on impressions.

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