Lens distortions and light leaks.  It’s called “Lens Whacking“. Over the years indie filmmakers came up with a way to make incredible optical lighting artifacts inside the camera by removing the lens while shooting, then hovering it over the sensor to allow light to come in, thus creating an on-the-fly dreamy light effect.
Cineflare Lens Whack is a realistic “lens whacking” and distortion and light tool for Final Cut Pro X.