Frame Rates: The Basics
The term ‘frame rate’ refers to the number of individual frames or images that are displayed per second in a film, TV or computer game display. The frame rates used for film and TV are standardised by the Society of Motion Picture and Television Editors (SMPTE).
Since 1927, the standard frame rate for film has been 24 fps (frames per second). For TV the standard is 30 fps for NTSC (National Television System Committee – the system used in North America, Japan and many other areas around the world), 25 fps for PAL (Phase Alternating Line – the system used in Europe, parts of Africa and SE Asia).
24 fps is not the minimum required for persistence of vision – our brains can make a continuous moving picture with as little as 16 fps – but it was a rate that gave a quality effect at a reasonable cost (higher frame rates would require more frames meaning filmmakers would use more film).
This means that for films to be transferred to video and shown on TV, the frame rates need to be adjusted. When something is being filmed specifically to show on PAL, frame rates are adjusted during the shoot with cameras running at 25 fps instead of 24. Alternatively, it is done at the time of transfer, with the film just run at the extra frame speed. For NTSC, where the difference is greater, this is done by a process called 3:2 pull down.
The future of frame rates
Recently, there has been a move towards using higher frame rates for movies and it became a hot topic in 2012 with the release of The Hobbit. Director Peter Jackson shot the film at 48 fps, twice the normal speed, as he argued that it made a clearer film (especially for 3D). If the camera is capturing twice the number frames more detail is captured, removing motion blur and strobing of fast moving action, but it was met with criticism.
Research into the field of consciousness perception has suggested that the human brain perceives the real world at a rate of around 40 conscious moments (frames) per second. The problem with The Hobbit was that it was providing too much ‘reality’ for a film.
Cinema-goers have been conditioned to the look and feel of a 24 fps film. The Hobbit went so far beyond this that it caused what is known as ‘The Uncanny Valley’ effect in viewers. This psychological concept says that if people are seeing something artificial, which starts to approach something looking real, they begin to inherently reject it. It’s the problem computer graphic animators constantly struggle with (think of films like The Polar Express) where as they try and make characters seem more realistically human, the effect can actually end up being quite creepy.
The Hobbit strayed into the Uncanny Valley because the extra information the film was displaying stopped it looking like a film and that made all the usual film conventions – the way scenes are lit, the way people look, etc. – seem oddly out of place and, some argued, more fake.
However, high frame rates are still being talked about by directors, especially 3D enthusiasts such as James Cameron, who is shooting Avatar 2 at 60 fps. For Cameron, the higher frame rates are all about maximising the effect of 3D. “3D shows you a window into reality; the higher frame rate takes the glass out of the window,” said James Cameron in an interview with Hollywood Reporter.
The implications of high frame rates
One of the most basic implications higher frame rates will have for producers is handling the ever increasing amounts of data it will produce. We’ve talked before about the effect of 4K. Quadrupling the number of pixels in a frame will already have an enormous effect. If you then double the number the number of frames, those will be huge video files, hard to store and even harder to move around.