editing.

Real background blur comes from the lens and cannot be added later. What software does instead is a convincing imitation, and knowing the difference tells you when it will look wrong.

Cutting yourself out is the easy half. Making the result look photographed rather than pasted is the half that gets skipped, and it comes down to two small additions.

A simple test decides it: is the information still in the file? Background, light and crop are recoverable. Focus, motion and a cropped crown are not.