Why can mobile phone night scenes and professional photos be pre-positioned?

It may be more convenient to take a selfie on the front, but isn't it convenient to take a selfie on the front of a mobile phone? Mobile phones are limited by the size of photosensitive elements. In the low light environment, the mobile phone is a short board with congenital defects. Although the cameras of mainstream mobile phones have reached 6.5438+0.3 million pixels, even 50 million pixels. However, the improvement of pixels does not bring about the improvement of image quality, but only increases the size of the picture. On the contrary, high pixels did not improve the image quality in low light, but declined. Why? Because the higher the number of pixels, the denser the pixels on the photosensitive element, so the size of each pixel becomes smaller, and noise is more likely to appear. This is a great test for the already small cell phone sensor. In the past, many SLR cameras only had 6.5438+million pixels, not to say that the pixels could not be improved, but to ensure the compromise of image quality.