Controlling Frame Rate without Expensive Cameras
The frame rate of video determines what its speed will be when it is played back. Normal play back speed is usually 30 frames per second. Some video formats and film play back at 24 frames per second. If the video was recorded at a frame rate different from the play back rate then your video will either have a high speed or slow motion effect. This effect is traditionally achieved in camera. Unfortunately, not every camera out there allows you to change the frame rate and the ones that do are usually expensive. But in reality anyone with a decent editing program can pull off this effect.
High speed is achieved in camera by slowing down the frame rate when recording. If you were to record an action that's ten seconds long at 15 FPS then it will play back in high speed for five seconds. You can create the same effect in your editing program.
Most programs have an option to change the speed of a clip. When you change the clip's duration to a length shorter than its normal running length the program compensates by removing frames. So if you took a ten second clip and changed the duration to five seconds the program will remove every other frame. It will create 15 frames / second video.
However, doing this will eat up more hard drive space than the in camera effect would. You need to store the ten second video plus a preview 5 second video that needs to be rendered for smooth play back. Thus, you have fifteen seconds of video stored for a five second clip. But it's still cheaper to do it this way.
High speed can be achieved in editing instead of in camera without a sacrifice to quality, but slow motion is different. Slow motion created in camera looks a lot better than slow motion created on the computer. When slow motion is done in camera it records the video at a frame rate that's faster than play back speed so that when it is played back it appears slow. For example, ten seconds recorded at 60 fps will take twenty seconds to play back at 30fps.
When you create this effect in an editing program the computer duplicates and adds frames to the clip to make it seem longer. If you were to make your ten second clip become twenty seconds then each frame would be duplicated. You would essentially have play back of 15 frames a second instead of 30.
But if the effect was done in camera then you would have an individual unique frame for the entire slow motion sequence. Slow motion achieved in camera is superior in quality to slow motion achieved in editing.