Video Formats and Frame Rates 1

On Sunday - 13th November, 2011

This is some info that I usually present in my first edit class.  With the everchanging formats and codecs that we use in HD film and video making editors , more than ever, have to understand frame-rates, formats and codecs.

This info is for people just starting in film & video or just getting into editing in a more serious way, for the experienced film makers and editors most of this info you will already know, but surprisingly I have found amongst even some of my quite experienced students there are a lot of people who don’t know the basics of this material.

 

Film Frame Rates – Sometime early in the end 19th Century it was discovered that if a series of images in sequence are shown at a particular rate there will be an illusion of movement.  A number of devices were created using this principle. Such as the Zoetrope invented by William Horner in 1834.

With the advent of film it was found that 24 frames per second gave a smooth and convincing illusion of movement and this became the standard frame rate used in film for many years.  Although other rates were sometimes used to save film especially on smaller cameras such as Standard 8 or Super 8, which often used 12 or 18 frames per second but slower frame rates could make movement look jumpy.

In animation a slower frame rate would be used to save drawing more frames than necessary. Often there is a dope sheet, which lays out the required frame rate for each scene.  If there is very little movement in the scene then only a few frames per second might be required if the is fast action like a fight scene then more frames are needed to give smooth motion.

With the advent of TV the frame rate was chosen in accordance with the cycle of the electricity system.  In Australia and Europe a 50hz system was used so we had a system called PAL using 25fps interlaced.  In America they had 60hz electricity and so had a system called NTSC based on 30fps(29.97fps) interlaced. These frame rates are what the Standard Definition  formats of PAL and NTSC were based on. Another system called SECAM is used in Europe that is also a 25fps system.

 

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