Photographer asks for help: Why is the reflection of still life taken with background paper serious? What happened? Why is the background paper also reflective?

Did you forget that I used a black sponge as the background? That's it. I also want to make sure that the light doesn't shine on the sponge.

You can't use bright paper as the background, even if the light doesn't directly hit the background, reflection is inevitable.

Measurement should be measured by points, not by averages. The stupid way is to use manual mode. The aperture, shutter and sensitivity are all manually adjusted, and the correct exposure can be determined after several fumbles.