The Xiaomi Mi 4s features a similar 5" Full HD IPS display to the one we saw on the Mi 4c. It has 441ppi for pleasantly sharp screen contents. Xiaomi says both sheets of glass on the Mi 4s are scratch resistant without specifying their brand or maker.
Taking a closer look at the display under our digital microscope reveals a standard RGB arrangement of the sub-pixels that make up the Xiaomi Mi 4s LCD panel.
The maximum display brightness of the Xiaomi Mi 4s (475nits) won't turn any heads, nor will the average contrast ratio of 975:1. The blacks are deep enough for an otherwise pleasant viewing experience.
The minimum display brightness is incredibly low at 0.6nits, which is perfectly suitable for late-night reading in a dark setting.
Regarding color accuracy, the Mi 4s screen is less than stellar with an average deviation (DeltaE) of 5.6, which shows the screen has less than perfectly accurate color rendering. We've seen worse even in flagship devices, so this one sits somewhere in the middle. For a screen to be considered properly calibrated it needs to have a maximum DeltaE of 4 and obviously, the lower the deviation, the better.
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The sunlight legibility of the screen is hardly spectacular, but you won't have any problems using the phone outdoors if you avoid direct sunlight.
Xiaomi has put a 3,260mAh battery inside the Mi 4s, a solid capacity for a 5" device. In our battery test, the Xiaomi Mi 4s scored a 75h rating, which means you can count on a little over three days if you do an hour each of calling, browsing and video playback a day. The phone did well in all three of our individual tests and it had a low battery draw in standby as well.
Opting for using the device with two SIM cards will clip some four hours off the total endurance rating.
That is of course solely based on the two SIMs drawing battery in standby - using an estimated power usage to make our battery results comparable across devices.
Xiaomi is providing a proper fast charger (5V/2A, 9V/1.2A, 12V/1A) in the retail box, which is nice. In our 30-minute charging test, the provided charger was able to charge the battery of the phone from 0% to 32%.
The battery testing procedure is described in detail in case you're interested in the nitty-gritties. You can also check out our complete battery test table, where you can see how all of the smartphones we've tested will compare under your own typical use.
The Xiaomi Mi 4s supports 7 LTE bands (the Europe's most common FDD LTE band 20 800MHz is missing though), and you can tap to an LTE network on either SIM, but the other will default to a GSM band. The Mi 4s also offers quad-band GSM connectivity and tri-band 3G connectivity with HSPA support.
The rest of the wireless connectivity features include dual-band Wi-Fi a/b/g/n/ac support and Wi-Fi Direct. There is also support for Bluetooth 4.1, GPS and GLONASS. Wireless screen mirroring is available via the Miracast protocol.
The IR blaster is located at the top and, coupled with the right software, you can use it to remotely control pretty much any IR controlled home appliance. Xiaomi provides its own MiRemote app, which supports a long list of devices right out of the box.
The Mi 4s is Xiaomi's third device to support USB Type-C - it's the new reversible connector for USB that builds on USB 3.1.
If you'd like to use USB OTG functions on the Mi 4s, you'll have to buy a third-party USB OTG adapter.