Canon 500D, using TV mode, same subject, same angle, why is the exposure particularly different?

Maybe you use spot metering, and the slight difference in focusing will lead to completely different metering results, which are completely different from the conditions on the spot. If you hold it, it is easy to encounter such problems. If it is on the shelf, it should not appear.

The TV is in shutter priority mode. If the metering point is dark, the system will automatically open a large aperture, which has a small depth of field. Objects that are not in the same focal plane of the focused object are prone to blur. And there will be a bright picture. If the photometry is on, the system will use a small aperture with a large depth of field, and the photo image will be more realistic, but it is also prone to dark images.

You can do a test by evaluating photometry, which should improve the stability of photo brightness a lot. But I can't get some results.