Simplify the following text for a Grade 6 native English-speaking person.
Original: With the standard practice of `` doubles '' or `` twos '' ( double-framing , exposing 2 frames for each shot ) , 12 changes are usually made for one second of film movement .
Simplified: Animation usually uses `` doubles '' or `` twos '' ; that is using two frames for each shot . This means that 12 changes are made for one second of movie .