What is the phenomenon of diffraction?

When light passes through some narrow holes or small holes, the light waves will disperse at the edge of the object. This optical phenomenon is called "diffraction".

From a photography perspective, diffraction will occur when the aperture is too small, causing the green edges of the image to become loose. This is a basic characteristic of light waves and has nothing to do with the optical quality of the lens.

Moreover, diffraction can also cause purple fringing in digital cameras.