What is the "Jiao Wai" of the lens?

Jiao Wai is out of focus, especially when taking portrait photos, I like to pursue the soft and fuzzy effect of Jiao Wai to highlight the theme. People usually hope that the fuzzy part of "blurred background" is Jiao Wai. Generally speaking, the shallower the depth of field (the larger the aperture, the longer the focal length), the more out of focus, the more blurred. Of course, this is also related to the distance between the background and the subject. Different lenses, even if the same focal length is in the same aperture. This is also an important indicator that many people prefer one shot to another. This is mainly related to the quality of the lens itself (including many aspects: coating, structure, lens itself and so on. ) is also related to the number and shape of aperture blades. Jiao Wai's light spots can be seen clearly, some are hexagonal, some are octagonal and some are round.