I've judging the low-light performance and image quality parameters based on Moto G5 Plus samples images that I've seen on dpreview. This is a very reliable resource so I know that these are in fact camera samples taken with the Moto G5 Plus and not another camera. The web is full of fake images and videos that people say they have taken with the Moto G5 Plus, but they aren't real.
Anyways, the Moto G5 Plus features a Sony Stacked BSI CMOS sensor with 1.12-micron pixels. The best news is that it comes with a f/1.7 aperture lens. This is a very fast lens, same bright aperture used in the Samsung Galaxy S7, and once of the reasons the S7 performed so well in low-light conditions. I was very impressed with the camera samples that I've seen on dpreview. There was one particular images that was shot at ISO 500 and 1/15 shutter speed. The image looked really well lit, considering there is very little ambient light and it was taken in when the sun sets. The image wasn't sharp when I viewed it in 100% magnification, but this is probably due to the lack of OIS in the camera.
The OIS is very important when shooting in dim lighting conditions, in the evening or in dark indoor places. The Samsung Galaxy S7 comes with OIS and tis is yet another reason why it performed so well in low light.
The Lenovo Moto G5 Plus also did well in terms of noise. There is certainly noise in the image, but it's mostly visible in the dark areas, whether in the brighter areas it's much less visible. I'm judging it based on an image shot at ISO 500. It's pretty darn good performance considering the sensor's small pixel size. There is another image of a church shot at ISO 640 and it also looks really clean in the bright sections of the image, and very good in the mid-tones and the dark areas of the photo as well. This is what you get when you deploy a camera with a very bright F1.7 aperture lens.
As you can probably tell, I'm very pleased with the Motorola Moto G5 Plus sample images' image quality in low light. I'm sure it could have performed even better with 1.4-micro or bigger pixels. I wonder if I'll get to see a flagship camera that dares to got under 10MP, with a 1/2" sensor, a f/1.7 aperture lens and OIS—The low-light performance could be out of this world. Of course phone vendors are restricted to sensor that those sensor's manufacturer produce, like Sony's and Samsung. Having a custom camera sensor designed specifically for a single or two phones would make the manufacturing much more expensive and the phone's price even more. It's not that I'm spoiled, I just see the potential of a different configuration that can beat any phone camera out there. All Sony needs to do is so come with a 1/2.3" Memory Stacked BSI sensor with a 8MP resolution and attach a fast lens to it, and I'm sure it would easily outperform the Google Pixel.
So bottom line, sterling low-light performance coming out of the Moto G5 Plus primary camera. It could have been better if there was an OIS system onboard, but hey, we can't get everything we ask for.
Check out the Lenovo Moto G5 Plus camera sample here on dpreview.com. I'm sure that soon we'll get to see much more low-light camera samples that will showcase how good this camera is for taking shots at night. I was very pleased with what I've seen sofar.