The Redmi Note 4 has a 13 megapixel BSI CMOS camera with f2.0 aperture, 5 element lens, and phase detection autofocus. It can also record 1080p30 and 720p120 slow-motion video. A two-tone dual LED flash is provided for illumination in the dark. On the front is a 5-megapixel sensor with f2.0 aperture and 1080p30 video.
The camera application on the Redmi Note 4 is same as on other Redmi phones. It's important to mention the 'Redmi' part as Xiaomi continues to make the distinction between Redmi and Mi series phones when it comes to the camera application, with the latter getting all the best features. The Redmi camera application, for example, has a stripped-down Manual mode that only lets you adjust the white balance and ISO, with no focus or shutter speed control, making it generally useless. There is also no HDR Auto option, with on and off being the only choices available. Fortunately, everything else is there, including the filters, camera modes, and the beautify options for the front camera.
The main camera performance on the Redmi Note 4 is good. The big improvement over the Redmi Note 3 is in color performance. While the Redmi Note 3 captured relatively flat and bland colors, the Redmi Note 4 consistently impresses with rich, warm colors, which are occasionally a touch too warm but nevertheless look good.
In terms of detail, the Redmi Note 3 has a slight advantage due to its higher resolution sensor but the Redmi Note 4 isn't far behind and unless you plan on cropping the images heavily the resolution disadvantage isn't a concern. As for dynamic range, the two phones were usually on par with the older Redmi Note 3 occasionally edging ahead as the Redmi Note 4 has a tendency to produce a punchier, more contrast-heavy image which hurts the dynamic range a bit. The HDR mode works quite well to restore some of the lost detail, however.
Lowlight performance too is acceptable but there's not much of an improvement here over the predecessor, with both phones producing decent results. The Redmi Note 4 does have slightly better autofocus performance in low light, as the Redmi Note 3 can occasionally miss focus. Both phones have a night mode that can clean up image further as long as you hold the phone steady.
The 1080p video performance was a mixed bag. The image quality and level of detail are fine but the dynamic range isn't impressive and the focus also tends to hunt a lot with moving objects. There's also no stabilization, optical or electronic, to smooth out camera shake.
One of the highlights of the Redmi Note 3 was the exceptional battery life. With the Redmi Note 4, Xiaomi aimed even higher, with the official claim being 25% longer battery life. This was achieved with a combination of a more efficient processor and slightly larger battery.
And for most parts, Xiaomi's claim stands. While your mileage may vary depending upon the usage and the activities being performed, by and large, we got around 20-25% improvement in battery life on the Redmi Note 4. While the Redmi Note 3 would give us around 7-8 hours of screen-on time on daily use, the Redmi Note 4 would easily last about 10-11 hours with roughly the same usage. This is impressive, considering there is not much of a performance penalty in achieving the higher battery life and the actual battery itself isn't that much bigger.
As with the Redmi Note 3, the Redmi Note 4 does not employ any kind of fast charging mechanism, taking two and a half hours to charge completely with the supplied 10W charger. This is roughly identical to how long the Redmi Note 3 takes to charge.
When Xiaomi announced the Redmi Note 4, we had our doubts that it may just be a case one step forward, two steps back over the Redmi Note 3. The Snapdragon 650 processor was one of the star attractions of the device and dialing it back in favor of the Snapdragon 625 on the new model seemed like a significant drawback on paper.
Well, we are glad we are not in the business of reviewing spec sheets because the reality couldn't be further from the truth. The Redmi Note 4 is not just an improvement in every other way, even when it comes to the performance from the new chipset it still managed to impress us, with everyday performance being on par with its more powerful predecessor to the point where it hardly made any difference. When you combine that with the fact that you now get a better design, better display, better camera, better battery life, and just an overall more refined and sophisticated experience and suddenly the new device looks like a win-win, as it very well should.
Last year, the Redmi Note 3 ran away with the crown of the budget smartphone of the year; a most well-deserved victory. This year, even in the face of rising competition, Xiaomi manages to hold its own with a highly competent, all-round smartphone that still offers the best bang for your buck.