Smartphone makers have been working on the bezel-free, all-screen design for years. In doing so, they have had to come up with ways to either shrink, eliminate, or relocate components that take up space on a handset’s face, such as the home button, proximity sensor, fingerprint scanner, earpiece and selfie camera. The biggest challenge of that mission so far has been the selfie camera. It is a major reason the iPhone has that infamous notch and the sole reason recent Android phone screens had a hole drilled into them. But phone brands may have finally found an answer with the nascent under-screen camera technology, which sees the selfie camera placed underneath the display panel. Chinese brand ZTE was the first to bring this technology to market, in 2020, albeit in flawed form. Korean electronics giant Samsung introduced its own version in the Galaxy Z Fold 3 this month, although that camera is so lo-res it’s meant as a backup option. It is instead rising Chinese smartphone maker Xiaomi that has released the first truly functional under-screen camera technology in its Mix 4 phone. It’s still not perfect, but it is the first sign that this technology is not a gimmick. Design and hardware Just about every flagship smartphone these days is well constructed with a premium in-hand feel, but the Mix 4 is even more polished than most, thanks to its unibody ceramic frame. Look at the back of an iPhone or a Samsung and you’ll see a seam where the back glass plate meets the aluminium chassis – that line doesn’t exist in the Mix 4 because its back and sides are a single piece. Xiaomi says it’s got the ‘perfect’ under-display camera on a phone Flip the Mix 4 around and you’re greeted with a 6.67-inch, 120Hz OLED screen that’s uninterrupted. The 20-megapixel selfie camera is still in its usual spot near the top middle of the phone’s face, it’s just hidden behind the screen. Software and features So how can the camera see clearly through a display panel? The trick is to reduce pixel size in the section of the screen covering the camera, leaving enough gaps between pixels for light information to pass through to the sensor. The image information that passes through is obviously not clean (it’s as if we looked through a slightly dirty window), so Xiaomi’s software has to do a lot of work cleaning up the shot in post-processing. Both the ZTE and Samsung versions of this technology are imperfect, with visible marks on the part of the screen covering the camera that the user can see with the naked eye. Samsung’s camera is also a paltry four-megapixel shooter. Xiaomi was able to make its selfie camera nearly invisible from the outside with transparent sub-pixel circuitry. The Mix 4 is also the first phone to hit the market with the brand new Snapdragon 888+ processor. It’s only a slight upgrade over the existing Snapdragon 888, but technically speaking, the 888+ is the new top dog Android processor. Xiaomi removes antitheft feature from flagship phone just days after launch The Mix 4 runs on Android 11 with Xiaomi’s MIUI version 12.5.4 on top. Since the Mix 4 is only sold in mainland China for now, it does not ship with Google apps pre-installed, but they can be easily downloaded from Xiaomi’s own app store. Performance and battery life The Mix 4 is absolutely top notch in processing power, overall UX fluidity, speakers and haptics. Battery life can be considered good too, able to last a full 12 hours with heavy use. The main triple-lens camera system, however, is good but not Xiaomi’s best. While the 108-megapixel main lens, 13-megapixel ultra-wide-angle lens, and 8-megapixel Periscope zoom lens perform well in a vacuum, they fall short on image sharpness, light intake, and zoom range compared with their counterparts in Xiaomi’s Mi 11 Ultra phone. But let’s get back to the star of the show, that under-screen selfie camera. Most people attempting a selfie for the first time will probably be alarmed, as the image in the viewfinder looks hazy and soft because the camera is covered by a display panel. But snap the shot and Xiaomi’s post-processing image algorithms do a great job of sharpening details and balancing dynamic range. In fact, if you snap the selfie and then immediately tap on the preview, you can see the changes in real time. Under optimal lighting conditions – good lighting that’s mostly directed towards the user’s face – the Mix 4’s selfies are almost as good as those taken using a normal selfie camera. But shoot in tougher lighting conditions – against backlight, or in low light conditions – and the shots suffer in quality. It is a reminder that, while Xiaomi’s under-screen camera solution is clearly superior to other companies’ takes on the technology right now, it still can’t beat a traditional selfie camera. Samsung’s new foldable phones first impressions: tougher, slimmer, cheaper Conclusion Some will wonder what the point is of putting up with a compromised selfie camera just to get an extra 0.5 per cent of screen space. It’s a fair comment, and given the choice now, I’d settle for the hole-punch design too. But Xiaomi’s Mix series has always been branded as a concept line, which Xiaomi uses to push the boundaries. Besides, there really are users who find the hole-punch cut-outs annoying. The good news, despite the new processor and cutting-edge tech, is that the Mix 4 isn’t expensive by flagship smartphone standards. In China it starts at 4,999 yuan (US$770).