Short · Cameras
Why do propellers look bent on camera?
Phones read the sensor row by row over about 1/50 s. A fast propeller swings around during that time, so each row catches the blades somewhere new and straight blades come out curved.
Try it yourself
Opens Shutter Lab. Change the same thing yourself.
Transcript
Why do propellers look bent on phone cameras? Your phone doesn't snap the whole picture at once. It reads the sensor row by row, top to bottom, over about a fiftieth of a second. A slow propeller barely moves in that time. Now spin it faster. By the time the camera reaches the bottom rows, the blades have swung around, so each row catches them somewhere new, and straight blades come out curved. Try it yourself at Explainer Tools dot com.