What frame rate are movies shot at?

By Benjamin Craig, Filmmaking.net

Traditionally, films have been shot using a frame rate of 24 frames per second. Although this may seem like an arbitrary number, it is actually a historical remnant from when sound was first introduced to movies back in the 1930s.

Prior to the introduction of sound, all films were shot at 18 frames per second. This rate was chosen because it was the lowest speed at which you can project a series of images and evoke a phenomenon in the viewer's eye known as 'persistence of vision' - where the gaps between the still images are no longer seen by the eye, thereby giving the illusion of motion. Film stock has always been expensive, so early movie pioneers did not want to spend any more on stock than absolutely necessary. Hence settling on the minimum framerate that would work. This also is the reason why silent films appear to be in 'fast motion' when played back today (a film shot at 18fps but played back at 24fps will appear to be sped up).

However, with the introduction of sound, 18fps meant the film moved through the projector too slowly to play back sound with a natural pitch. This is because early film sound was optically printed onto the stock next to the image and read by a sound head in the projector. In keeping with the cost-saving mentality, 24fps was chosen as the new standard because it was the minimum speed at which sound could be played back at a natural pitch, while at the same time minimising the amount of film stock (and therefore cost) of shooting a film. And thus the standard frame rate remained at 24fps for over 80 years.

Of course, video has historically used alternative frame rates due to the fundamentally different way in which it captures images when compared to film. The two main video standards are NTSC and PAL. NTSC captured images at 60 fields per second (with a field being 'half' a frame), giving an effective frame rate of 30fps (actually 29.97fps for reasons of interest only to video engineers). PAL captured images at 50 fields per second, or an effective frame rate of 25fps.

However many filmmakers believed that 24fps offered a more 'cinematic' look for their work, so not long after the digital revolution began, video cameras capable of shooting 24fps appeared. Instead of capturing with two fields, these cameras were able to capture the image in a single progressive frame (hence the rate being referred to as 24p) which mimics the way film captures images.

Recently, some elements of the film industry have begun to get excited about the potential of high frame rate (HFR) cinematography. Proponents include James Cameron and Peter Jackson, whose "The Hobbit: An Unexpected Journey" was the first major film to shoot and be exhibited in HFR - in this case, 48fps. James Cameron has also indicated his interest in 60fps HFR. Whether these formats have a future is yet to be seen, as the release of "The Hobbit" has divided both industry and audience, with the detractors pointing to the fact that the hyper-real nature of HFR 'cheapens' the look of the film and reduces the 'cinematic' feel.

Last updated 16-Dec-2013

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