I personally wasn't impressed at all with the Xiaomi Redmi Note 3 front camera quality. I did viewed many sample images and analyzed the image quality. I wanted to know how good the Redmi Note 3 front camera is. Before I share my opinion and explain why I put it in the cons section, let's first take a look at the Redmi Note 3 front camera specs.
The Xiaomi Redmi Note 3 features a 5MP front-facing camera. It uses the Omnivision OV5670 1/5" PureCel sensor with 1.12-micron pixel size. This sensor was revealed on May 6, 2014. Just in comparison, the front camera of the Redmi No 4 has the same 5MP resolution and the same sensor size but uses a Samsung S5K5E8 BSI CMOS sensor. Regarding the lens, the front-camera features a f/2.0 aperture lens with 85-degree field of view.
I was first excited to see a front camera with 5-megapixel resolution, but then looking deep into the specs I've found out that it actually uses a very small 1/5-type image sensor, therefore the pixels on the sensor are very small. The active image size is 2.828 mm (H) by 2.128 mm (v), it's a very small sensor. Omnivision is marketing this sensor has one with superior low light performance. This sensor was designed to be used for front and rear camera placement in mobile phones and be cost-effective.
According to the official sensor document, the OV5670 can achieve the same light sensitivity and SNR as some of the 1.75-micron pixel sensors (according to the official specs, the max S/N ratio is 35.6db) and also full-well capacity as the previous generation 1.4.micron pixel sensors.
Regarding the PureCel technology. This is an Omnivision uses a stacked die technology that should be equivalent to Sony's Stacked BSI technology where the imaging array is separated from the image sensor processing pipeline.
So how all this translates to image quality?
After inspecting many sample images taken with the Xiaomi Redmi Note 3 selfie camera, I saw that it captures relatively soft images that lack punch and sharpness. I was surprised however that it was able to hold noise levels down quite well up to around ISO 600, like in this image by gadgethouse.com that was shot at ISO665 with 1/33s aperture. The fast f/2.0 aperture lens also help in promoting better low-light performance and it's certainly needed to help keep the ISO sensitivity level down. I couldn't ignore the low dynamic range which in mixed lighting conditions and high contrast images you can clearly see that the sensor has problems maintaining details in the shadow areas.
The Xiaomi Redmi Note 3 front-facing camera does work well in daylight, but still leaving a lot to be desired. Just in comparison to a high-end smartphone, the Samsung Galaxy S7 edge also comes with a 5-megapixel front camera, but the specs are much more impressive. We are talking about a Samsung S5K4E6 that utilizes Samsung's advanced ISCOCELL technology. The sensor is large measuring 1/4-inch and boasts large pixels, measured at 1.35-micron. Added to that is a very fast f/1.7 aperture lens. This gives you a night and day performance compared to the Xiaomi Remi Note 3, but of course the Redmi Note 3 is a much cheaper smartphone, so does its camera specs.
Here is a sample video taken with the Xiaomi Redmi Note 3 by Inspire2Rise YouTube user.
You can see that the image quality in shaded area is pretty good. I've seen some comparison that compare the Coolpad Note 5 vs the Redmi Note 3 and the selfie camera of the Coolpad Note 5 easily outperforms the Redmi Note 3 one with higher dynamic range, better low-light performance and much brighter images overall (can be seen here). I was quite surprised that the Coolpad Note 5 was able to outperform the Note 3 sensor with its slower aperture lens an higher megapixel resolution, but this just leads me to believe that there is a better sensor there.
So overall there isn't anything to be excited about the Xiaomi Redmi Note 3. Regardless of everything I've read on the Omnivision OV5670 sensor, its performance didn't impress me a tiny bit. It can pull out some decent images given good lighting conditions but the image quality is just mediocre. I think that if you are already giving up on high resolution, at least give us a sensor with much larger pixels. I mean f/2.0 aperture is fine for a front-facing camera, but not too much can be done when you have such small pixels. So overall I'm quite disappointed with that image quality and there are better alternative out there as far as the front camera image quality is. I think that this realtively cost-effective sensor was used to balance the overall cost of the device