My SLR 650D, the picture taken when I first bought it is like this. Now it is a bit dark. The pattern on the wall is clearly visible but a bit dark. What is the reason?

Is it an automatic transmission?

The camera metering results are different depending on the subject.

It is normal for the phenomenon mentioned by the poster to occur!

In the first picture, the white wall is the background, and other objects occupy a large proportion of the picture. The metering data is biased toward "overexposure";

In the second picture, the white wall is the main subject. , there are basically no other objects, and the metering data tends to be "underexposed".