Why is the sunny scene shot by SLR overexposed in the bright part or too dark in the dark part?

This is because the tolerance of camera exposure is limited. There are about four files in the film age and only three files in the digital age, that is, from light to dark. Only those in exposure value for 3 consecutive files can be exposed normally, with over-exposure and under-exposure. It is also related to the processing of CMOS and graphics chips. The higher the detail, the higher the tolerance, which is also the essential difference between high-end and low-end cameras. What resolution and pixel value are fooled by ignorant consumers. The sensor tolerance of CCD will also be higher. For example, Leica M series, combined with high-resolution Leica lens, can record the details of a wider exposure range, which is one of the reasons why Leica is more expensive.

It is precisely because of this that the concept of "flash master" appeared, which relies on artificial light distribution to distribute light for dark parts and reduce the light ratio of the picture, thus solving the defect of camera tolerance through curves and recording all the details in the picture.