Xiaomi Mix 4 Hands-on: The original Mi Mix vision, finally realized to perfection

Xiaomi Mix 4 Hands-on: The original Mi Mix vision, finally realized to perfection

Xiaomi started making smartphones in 2011 — the Mi 1 was released on Aug 16 of that year. And while the company quickly achieved commercial success in its hometown China, it wasn’t really until October 25, 2016, that the company made a noticeable splash on a global stage and turned heads. That was the day Xiaomi unveiled the Mi Mix, a so-called “bezel-less phone” with virtually non-existent bezels on the top, left, and right sides of the screen. I still remember the headlines trickling out of western tech media that day, using words like “blows minds,” “made jaws dropped,” and “beautifully bonkers” to describe the device. It was the first time Xiaomi garnered such gushy praises from English media.


Of course, the Mi Mix wasn’t truly without bezels, as it sported a chin bezel that was needed to house the display controller parts and the front-facing selfie camera.

But smartphone innovations have come fast. Phone makers soon figured out how to roll the display controller bits under the screen to reduce chin bezel space, and selfie cameras wiggled their way to behind the display panel — it just needed a punch-hole cutout for the camera to see.

Eventually, brands figured out a way to not need that hole at all. OPPO introduced this tech first as a concept, ZTE then released it commercially with the Axon 20 5G, Samsung brought it to the globe with the Galaxy Z Fold 3, and now Xiaomi has adopted it for the Mix 4.

It took five years, but Xiaomi’s original vision with the Mi Mix — a truly bezel-less phone — has finally been achieved. Curiously, Xiaomi dropped the “Mi” part of its usual branding from the name of this device.

Mi Mix 4 back

Click to expand: Xiaomi Mix 4 Specs

Xiaomi Mix 4: Specifications

Specification Xiaomi Mix 4
  • Ceramic unibody
  • Corning Gorilla Glass Victus on the display
Dimensions & Weight
  • 162.65 x 75.35 x 8.02mm
  • 225g
  • 6.67-inch CUP AMOLED display
  • 2400 x 1080p; 400PPI
  • DCI-P3, JNCD~0.34, dE~0.40
  • 120Hz refresh rate
  • 480Hz touch sampling rate
  • 5,000,000:1 contrast ratio
  • 10-bit TrueColor
  • Dolby Vision
  • HDR10+
SoC Qualcomm Snapdragon 888+
RAM & Storage
  • 8GB LPDDR5 RAM + 128GB UFS 3.1 storage
  • 8GB + 256GB
  • 12GB + 256GB
  • 12GB + 512GB
Battery & Charging
  • 4,500mAh battery
  • 120W wired fast charging
  • 100W wireless fast charging
Security In-display fingerprint scanner
Rear Camera(s)
  • Primary: 108MP 1/1.33″ HMX sensor, 1.6μm 4-in-1 Super Pixel, OIS, 7P lens
  • Ultra-wide: 13MP, free-form lens, 120° FoV, 6P lens
  • Telephoto: 8MP periscope, 5x optical zoom, 50x digital zoom, OIS
Front Camera(s)
  • 20MP CUP camera, 1.6μm 4-in-1 Super Pixel
Port(s) USB Type-C
  • Stereo speakers tuned by Harman Kardon
  • Hi-Res Audio certification
  • Hi-Res Audio wireless certification
  • 5G
  • Wi-Fi
  • Bluetooth
  • NFC
  • IR Blaster
Software MIUI based on Android 11
Other Features
  • X-axis linear motor
  • UWB point-to-connect
  • Graphene cooling solution

About this hands-on: I received the Mix 4 from Xiaomi HQ for review. Xiaomi did not have any inputs in this article

Xiaomi Mix 4: Under-screen Camera

We have to start with that selfie camera. Dubbed “CUP” (camera under panel) by Xiaomi, this 20MP camera is placed in the center-top part of the Mix 4’s front-side, underneath the display panel.

Just like the implementation in the ZTE Axon 20 and Samsung Galaxy Z Fold 3, the technology sees pixels in that particular part of the screen covering the camera lens be shrunken to allow light information to pass through the lens.

A rendering of Xiaomi’s CUP technology.

A rendering of Xiaomi’s CUP technology provided by Xiaomi.

But while ZTE and Samsung’s implementations (in the Axon 20 5G and Galaxy Z Fold 3) leave a mark on part of the displays that can be easily seen, Xiaomi’s implementation is much harder to notice.

Here’s the Mix 4 display showing various images and colors at different angles. The camera area is almost invisible. I’ve just seen it pop up a couple of times at extreme off-center viewing angles, but this was me trying extremely hard and look for it.

But how does the selfie camera perform? I’d use the word “okay.” Because the camera is ultimately still covered by a display panel, there’s a consistent hazy look in the camera viewfinder when previewing selfies. This is slightly noticeable if you shoot in favorable lighting conditions, like indoors with well-balanced lighting. But when shooting in tougher situations like against backlight, the viewfinder looks like I’m surrounded by smoke, and lights are all blown out.

But Xiaomi’s software fixes matters quite a bit in post-processing. If you snap a selfie and immediately view the shot, you can see the post-processing happening in real-time (the process takes about half a second). Here’s how the image looked in the camera viewfinder in real-time and how the final shot turned out.

When shooting in favorable conditions, the Mix 4’s 20MP selfie camera can still produce a solid shot that is only slightly inferior to “normal selfies” captured by other phones.

But in harsh shooting conditions, like a scorching sun right behind my head or dimly lit streets? The Mix 4 selfie images suffer in dynamic range, sharpness, and overall light intake.

Xiaomi's software fixes selfie camera haziness quite a bit in post-processing

Software updates could improve selfie camera performance in difficult lighting conditions, but it is imperative to judge the phone on what it can do right now. It’s fair to say that if we’re talking purely image quality and ignoring the engineering challenges, the Mix 4’s front-facing camera produces inferior shots to other recent top flagships. However, it’s worth mentioning that Xiaomi’s under-screen camera performs much better than ZTE Axon 20’s or the Samsung Galaxy Z Fold 3’s under-screen cameras though.

Xiaomi Mix 4: Hardware and Design

Mi Mix 4 back side.

Looking at the Mix 4’s overall design and construction, the words premium and classy come to mind. The Mix 4’s body is crafted out of a single unibody aluminum piece, meaning there isn’t that visible seam between the back plate and chassis that are present in most smartphones.

The 2400 x 1080 OLED screen measures 6.6-inches diagonally and refreshes at either 60Hz or 120Hz. It’s a good-looking panel, but not as ultra crisp as the screen used in the Mi 11 Ultra, and it also lacks the dynamic variable refresh rate seen on the screen of the Galaxy S21 Ultra.

Mi Mix 4 screen.

The Mix 4's body is crafted out of a single unibody aluminum piece, and it looks absolutely classy

Unfortunately, I find palm rejection to be below par on the Mix 4, as I have encountered several unwanted palm touches when handling the phone. Now I know curve screens haters are going to lecture me and say that’s why “curved screens suck,” but I did not encounter such issues with the Xiaomi Mi 11 or Mi 11 Ultra displays with similar curvatures, and Huawei’s even more drastic waterfall screens have exceptional palm rejection algorithms that never give me false touches. I am using a device that’s only gone on sale for 24 hours at the time of writing this, so I am hoping that Xiaomi will fix this issue via software updates soon.

Inside, the Mix 4 is powered by the Qualcomm Snapdragon 888+. Benchmark scores from Geekbench show that it is slightly more powerful than the Snapdragon 888. But in real life, I didn’t notice any superior performance. The phone runs fine, just like the Xiaomi Mi 11 ran fine. I must mention I’m not much of a mobile gamer, so maybe others will benefit from the newer and slightly faster SoC.

Mix 4 benchmarks

Mix 4 with Snapdragon 888+ and Galaxy S21 Ultra with Snapdragon 888

There’s a 4,500 mAh battery which can be topped up at 120-watt wired charging (charging brick included in the box!) and wireless charging up at 100-watt speeds if you use Xiaomi’s official charger (sold separately).

Xiaomi Mix 4: Rear Cameras

The Mix 4’s main camera system consists of a 108MP main camera using Samsung’s HMX sensor with a 1/1.33-inch image sensor, a 13MP f/2.2 ultra-wide, and an 8MP Periscope zoom lens with 5x optical zoom. Those who follow smartphones closely will be aware that these components are a bit lower tier than what Xiaomi used in its Mi 11 Ultra, and results show the difference.

Mi Mix 4 camera module.

While the Mix 4’s main camera keeps up well, producing shots with vivid colors, excellent dynamic range and even some of the Mi 11 Ultra’s awesome natural bokeh, the Mix 4’s ultra-wide camera, and zoom lens fall short of what the Mi 11 Ultra can do. It is still a very good camera system — just not Xiaomi’s absolute best since that bar is higher up. Still, this is nitpicking — most people who buy the Mix 4 will be happy with the camera, as all three lenses get the job done.

Compared to the Galaxy S21 Ultra, the Mix 4 camera holds up well in most conditions but loses in ultra-wide photos.

Xiaomi Mix 4: Conclusion

Even though the original Xiaomi Mi Mix got a commercial release inside China shortly after its launch, Xiaomi still continued to call it a “concept device,” probably because the company knew the phone was an experimental device with quirks (you needed to turn the phone upside down to take selfies, for example).

The Xiaomi Mi mix 4

The Xiaomi Mix 4 is, in my view, a return to that “concept device” philosophy. Xiaomi knows its under-screen “CUP” technology, however impressive as it is compared to other under-screen solutions, still can’t beat a regular selfie camera. But that’s okay because a “concept device” means it’s not meant for mainstream consumption just yet. It’s for enthusiasts to get a glimpse of an interesting idea executed in a specific way. I think this is why Xiaomi opted to release the Mix 4 in China only instead of pushing a global release. For the global market, Xiaomi’s top dog is still the highly polished, absolutely amazing, and overkill Mi 11 Ultra.

The Mix 4 is a flex on Xiaomi’s part for fans. It’s Xiaomi finally achieving the original Mi Mix’s vision: a truly bezelless phone.

About author

Ben Sin
Ben Sin

I'm a senior editor at XDA Developers. I have been a journalist for a decade, the last five years covering the mobile tech scene closely, reviewing just about every phone and attending trade shows and launches. I also run a gadget review channel on YouTube.

We are reader supported. External links may earn us a commission.