This can happen when you blink faster than the shutter on your camera
In this trippy photograph we see what happens when you blink faster than the shutter on your camera. The cause of this optical illusion is due to the camera using a “rolling shutter” in which:
A still picture is captured not by taking a snapshot of the entire scene at single instant in time but rather by scanning across the scene rapidly, either vertically or horizontally. In other words, not all parts of the image of the scene are recorded at exactly the same instant.
Photograph by Luke Mandle
[via Boing Boing via reddit]