The nubia Z11 mini S rear camera features a 23MP Sony IMX318 sensor. It's the same sensor used in the Asus Zenfone AR camera and Xiaomi Mi Note 2 camera, as well as other devices. So how good is its image quality?
Let's start with the specs. The Sony IMX318 is a 1/2.6-inch Stacked CMOS back-illuminated sensor that boasts 22.5MP effective resolution. From what I've read on Sony's website, this sensor that has 1.0-micron pixels can outperform the IMX230 that has 1.12-micron pixels. As you probably know, the pixel size doesn't tell the whole story about the sensor performance. The sensor technology continues to improve and the latest mobile sensors nowadays are capable of amazing image quality if you compare them to sensors a few years back. Of course a small sensor still suffer from the same problem, small pixels. Some companies try to enhance the image quality by using a dual-lens camera sensor, but the nubia Z11 mini S feature a single lens/sensor camera system, not two.
By the way, the nubia Z11 miniS has a different sensor than the Z11 mini (the non-S version). The Z11 mini comes with a 16MP Sony IMX298 sensor same as in the nubia Z11. The IMX298 sensor has very good performance when sufficient light is present, but falls short in low-light, regardless of all the technology features that I've seen mentioned on the official website. It's not bad, don't get me wrong, but you can definitely see that the small pixel has their saying if you know what I mean.
So now ZTE comes with its nubia Z11 mini S and stick a sensor with a ridiculous resolution. To be completely honest, I really think it's a really just a bad idea, I mean, who the hell needs a 20MP+ camera. It's not that many people go and make large prints of their images, most people share them online. For that, even a 2MP is way more than enough, you can even make really great small prints if you like to. No doubt that there are still many people out there that are still confuse between megapixels and image quality. Even Nikon and Canon in their Full Frame DSLR cameras prefer using sub 20MP to deliver better low-light performance.This resolution is good for a full frame camera, but not for a tiny sensor on a mobile phone. The only reason these cameras can perform well is due to the advanced technologies used in those sensor, but also because almost all mobile phones have a very fast prime lens which compensates for the lack of photons that each pixel can collect. There are even better technologies out there that can vastly improve the sensitivity of the sensor, but they are still not available because they are very expensive.
The nubia Z11 mini S will give you a very detailed image, no doubt about it, but only if you shoot at an optimal shooting conditions where there is enough light for the camera to work at its best. It would have been better if the camera had a faster aperture like f/1.7 instead of f/2.0, but this is not a high-end smartphone, so ZTE had to compromise on several features.
There are some software and hardware options that helps improve the low-light performance using the NeoVision 6, including a slower shutter speed option and having the option to capture images in DNG Raw file format.Raw file format holds more color information and can be used to enhance the image quality when this file is processed on your computer. A slow shutter speed can allow more light to enter the lens and produce better exposure for your images.
The main problem with the nubia Z11 mini S main camera is that it does not have OIS.This specific phone model could benefit from one by a large margin. An optical image stabilization would allow photographers to shoot at slower shutter speed and still maintain a sharp and focused image. You would at least gain a stop or two stops advantage, which could have improved the low-light performance by quite a large margin. Not having OIS means that the ZTE nubia Z11 mini S would become much less ideal for low-light photography.
OK, so how all this theory and specs translates to image quality?
In daylight the nubia Z11 mini S can capture stunning image with a lot of details and great color reproduction. I really love the colors in the sample images that I've analyzed, color accuracy is good, but the image is slightly over saturated to my taste, nothing big deal.
The low-light performance is average, and the camera is forced to shoot at very high ISO to compensate for the lack of light. I've seen sample images taken with the nubia Z11 mini S at night where there was still good artificial ambient light and the camera captures the image at ISO 4200. You can still get some really nice low resolution shots, but you are limited with what you can achieve with this camera in low-light conditions.
The nubia Z11 mini S is definitely a camera to enjoy shooting in bright daylight where it can really shine. I personally would have loved if the mini had a 8MP sensor with better low-light performance. It also seems that the image processing boosts the colors to make image more pleasant to the viewer. Of course there always an option to shoot in RAW file that can help you can even better image quality and get more precise control over how you want the image to look like in post processing instead of relying on how the camera want the image to look like using its predefined settings.
So overall the image quality is really good outdoors, color accuracy could be better but still not something that should trouble you. Images are very sharp and detailed but low-light performance is still limited due to the sensor small pixels and the lack of an optical image stabilization. For a phone that costs around $220, I think it's pretty good offering.