Starship Asterisk*

It's lighting and perception.

We're used to seeing lighting from above and indeed our brains are hardwired to interpret unknown lighting as being from above, since the sun is never below the observer in normal circumstances.

Simply flip the image 180 degrees and you'll see concave craters.

I sometimes have the same problem; it is to do with optics. You can stare at the image and see the crater as concave or convex but by noting the shadowing of the overall image will clue you as to concave or convex.

Why, when I look at photos of a body covered in craters, such as the recent one on APOD of Enceladus, do the craters seem to change perspective between being concave and convex?