This triple Leica camera is the key feature of this phone and what makes it so interesting. The Huawei P20 Pro features not less than three different cameras (Tri-lens camera). The first one is a 20MP monochrome camera with an f/1.6 aperture lens, a 40MP RGB-sensor (Bayer) wide-angle camera with an F1.8 aperture lens and lastly is a 8MP telephoto camera with an f/2.4 aperture lens.
The three cameras were design to give users the best of both worlds. So instead of going with either a monochrome+RGB combo or a wide-angle+Telephoto combo, Huawei put it all in one. This means that the cameras is design to deliver very detailed photos, with great contrast and fast focusing, perform good in low-light situations, provide a beautiful bokeh effect for your portraits as well as give you versatility so you can shoot in either wide-angle or telephoto, what best for the particular subject you are shooting.
The telephoto zoom lens provides 3x times the zoom of the wide-angle lens. Keep in mind that this is not digital zoom, the telephoto camera has different optical design that allows it to operate as an independent camera and give users the option to capture far away object without any image quality degradation.
Huawei is definitely taking the competition very seriously with its triple rear-facing cameras.
I have to admit that I am kind of worried about low-light performance of the wide-angle camera, the one with the f/1.8 aperture, because the pixels are going to be very small, which can negatively impact the low-light performance of the camera. Also F1.8 might not be that fast to compensate for that. The good news is that this camera is equipped with a large 1/1.7-inch sensor. Furthermore, the main camera uses Quad Bayer structure which means that the camera can used pixel-binning technology using 2 x 2 pixel units to take high-quality pictures in low-light conditions, but this compromises image resolution, which means that you get only 10MP images using this shooting mode.
So from what I can tell right now, no just that there is nothing to worry, we might even see pretty impressive low-light shots coming out of this 40MP sensors.
Overall, definitely a great advantage that the P20 Pro has over its peers. If you are an enthusaist photographer, you should certainly give the P20 Pro a look.