Sony H70, why do vignettes (black edges) appear on the corners of the camera? What's going on? Is it broken?

Don’t worry, there’s nothing wrong with the camera, it’s normal.

The imaging principle of a camera is similar to that of a convex lens, but it is much more complicated - the lens is often composed of n groups of n lenses.

A concave lens is circular, and its image is also circular, and the image formed by it is also similar to a concentric circle, with the brightest layers in the center becoming darker. This is the inevitable result of the principle of refraction

The camera, whether it is an electronic sensor or a film, is rectangular. Cutting a circle into a rectangular shape results in vignetting at the four corners.

Vignetting is inevitable, no matter how good the lens is, the difference is only in the degree of vignetting.