3:2 Pulldown Explained
What is 3:2 pulldown?
How do you stretch 24 frames of film onto 30 frames (60 fields of video)? You improvise. Basically, we stretch four film frames into ten video fields. Even if we simply doubled the film frames, we would still only have eight fields. So, we have to create two brand new video fields. In order to get the motion looking fluid, these new video fields are constructed using two different film frames. Confused? Take a look at the image below.
Click to see example of even and odd video frames »
Notice 'frame 3' and 'frame 4' are using images from two different film frames, one for each video field. Also, under the magnifying glass, notice that 'field 1' in 'frame 4' is drawing half the lines and 'field 2' is drawing the second half, making a complete picture.
If you watch your standard NTSC television, like most of us do in the USA, this is what you see. There may be the occasional visible line, or a flitter or a flutter here and there, but for the most part it is an acceptable form of entertainment. We are a resilient bunch aren't we? Well, we are also resourceful. We now have display devices like video projectors that can display even better images. These devices are not interlaced, but more like film, they are progressive. The image below illustrates progressive scan.
Our quest for the best film-like images has thrown yet another wrench in the wheel. We have successfully converted the film frames to video, but how do we get the video frames to look like film again? The answer, reverse the process.