Rendering look

Swirly bokeh

Swirly bokeh is when the blurred background seems to spin around your subject. It happens toward the edges of the frame. Every out-of-focus point of light is an image of the aperture, and for light arriving at an angle the front elements shade the rear ones, an effect called optical vignetting, so those discs get clipped into ovals that circle the center. It's typical of lenses built on the Zeiss Biotar formula and of old Petzval portrait lenses. To get it, shoot wide open, since stopping down two or three stops cures most optical vignetting, and put a busy background of small highlights, like leaves against the sky, behind your subject. A full-frame sensor shows the most, because a smaller sensor crops away the edges where the swirl is strongest.