What should I do if all four corners of the micro-single photo are black?

When 1.APS lens is used on Quan Huafu fuselage, because of the small image field of the lens, the edge will be stripped off, that is, the corners will be black.

2. Due to the cost factor, the image field of some lenses can't be made very large (including the Quan Huafu lens of Quan Huafu and the APS lens of APS). When the aperture is large, there may still be a certain degree of dark angle, and generally the dark angle will disappear when the aperture is reduced by one or two steps.

3. The influence of the lens hood or filter bracket.