3:2 Pull Down

3:2 Pulldown explained

Due to the incompatibility of television and film signals a system was devised to transfer from one signal to the other to limit the loss of image quality, this system is called 3:2 pulldown or Telecine (Pronounced Tele Seen).

The Problem.

Film has 24 frames per second (fps), while television signals (video) have 30 fps for NTSC and 25 fps for Pal. Film is also a progressive signal (the image is displayed in one hit )

Progressive Image displayed in one hit

 

While Video is an interlaced signal (the image is displayed in two hits one hit displays the even-numbered horizontal lines, the next hit displays the odd-numbered lines).

So you can see that when a film image is sent to a television the television has to convert the signal to be able to display it. But how to convert 24 fps to 30 or 25?

With 3:2 pulldown, four frames of film are converted into 10 interlaced video half frames, known as "fields." The first film frame is turned into three fields (3:); the next into two (:2), and the process is repeated. Sometimes, 3:2 pulldown is called "2:3 pulldown." This process is reversed to convert video to film.