How did we end up on a 24 frame per second standard, anyway? (Patreon)

During the 1890s through 1920s, the world of motion picture was an absolute wild west of competing formats and standards. For every Kinetoscope, Biograph, and Cinematograph, the formats developed and used by Edison, Griffith, and the Lumière brothers, there were a dozen Viventoscopes, Miroscopes, Birtaks, Biocams, Vitaks, and Cinéoramas, all with different combinations of camera format, film format, and projector format.

In terms of frame rate, these formats ranged from 16 to 40 frames per second, and even after the earliest chaos settled down and 35mm film became the standard size, different studios would intend for their silent films to be shown at kinda just whatever frame rate they preferred. 

Cameras during this time were almost entirely hand-cranked, even after electric motor cameras became available, because hand-cranked cameras could go places where electricity wasn’t available. They were lighter, smaller, and they gave the cinematographer direct, granular access to the manipulation of time by under cranking or over cranking. Go a little bit faster, things slow down, details take on more weight and importance. Go a little bit slower, things speed up, they become more weightless, chaotic, and silly.

While it’s commonly stated that the standard frame rate during the silent era was 16 fps in the oughts and teens and 18 fps by the '20s, in actual reality recording frame rates were all over the place. This was a product of both deliberate intent and simply because everything was hand cranked and no matter how good you are at keeping time it’s almost impossible to avoid wobble or make sure that you’re cranking at exactly sixteen frames per second and not fifteen or seventeen.

Thing is that studios and directors didn’t really care all that much because projectors were all variable speed. The director would tell the operator what speed to crank at for the effect they wanted, the operator would get as close as they could, within tolerances, then the director and the studio would watch the dailies and play with the speed of the projector until it looked the way they wanted it to and then write down the results.

Heck, in the studio system, for the vast majority of lost and forgotten films, the person making that call was more often than not the producer, who had nothing to do with the actual shooting, based the decision entirely on their personal sensibilities.

Films would then ship out to exhibitors with cue sheets that had suggestions for what kind of music the movie should be paired with, and instructions for what speed the projector should be set to, either implicitly by the rough lengths of the musical cues or a stated total runtime, or in explicit detail. For the biggest names in the business, like D.W. Griffith, these instructions might mean changing projector speed for different reels of the film, or even on the fly as the movie is playing.

So you have all these movies that are shot at different frame rates, then played back at different frame rates, often slightly higher than whatever the film was shot at. And then theatre managers, for their part, would often turn that up just a little bit higher so that the movies ended sooner, because if you can shave a couple minutes off of a feature then you can squeeze in another short.

It was absolute chaos.

Then sound was invented.

Now, the development of synchronous sound film is an entire discussion just on its own, a process starting in 1899 and spanning three decades of experimentation and technological advancement in multiple disciplines, but we’re going to jump straight to the early 1920s.

Synchronous sound presents two main technical demands:  the need for a constant frame rate, and the need for a minimum frame rate.

The need for a constant frame rate is pretty self-explanatory. If the soundtrack and film are playing at different speeds then they’re not in sync or won’t stay that way, and if you do keep them in sync by changing both of them equally, well, the human ear is far more sensitive to pitch changes in sound than it is to flicker changes in visuals.

Minimum frame rate is a bit more oblique. First, even if you have perfectly synchronous sound at 16 fps, the frame rate is a little low for satisfactory dramatic dialogue. There’s too many small, fast facial movements in speech, and 16 fps doesn’t quite catch these, and cues like that will actually call attention to how choppy the action is. Modern viewers would compare this to the footage from a webcam.

Second, the easiest way to ensure that the sound and the film remain in sync is to lock the two together, with the speed of one dictating the speed of the other, and at 16 fps the attached audio systems just aren’t moving fast enough for decent quality audio.

There were two competing approaches to sync sound, one used 16 inch shellac phonograph discs that were linked to the projector, and the other used an optical device to write the soundtrack onto the edge of the film with a companion reader on the projector. Both solutions ran into different roadblocks with a similar root problem.

At 16 fps a feature film reel is 1000 feet long and runs for just under 17 minutes and moves through the projector at 12 inches per second.

For the sound on disc systems like Vitaphone they needed to balance the speed the disc rotates (which has a direct impact on sound quality as it effectively translates into sample rate), the total runtime of the disc, and the physical size of the disc itself.

In 1920 it was really difficult to create a shellac disc that was 17 minutes long, and a reasonable diameter, and didn’t sound like ass. Increasing the frame rate would reduce the length of a reel making it easier to hit those other two marks.

For sound on film, the challenge had fewer variables but bigger hurdles. The brand new technology was much lower resolution than comparably mature phonograph technology, so at a baseline the audio quality was just worse. This coupled with the low sample rate of 12 inches per second made sound on film an interesting tech demo but unacceptably low quality. Increasing the frame rate had a direct impact on the quality of the attached audio.

Parallel to this, by the 1920s the chaos of playback rates had crept upwards, with films being recorded and displayed pretty consistently in the range of twenty two to twenty six frames per second.

Theatre managers in the rapidly expanding industry of the multi-screen movie palace, were demanding studios stick to a standard frame rate to reduce the amount of time projectionists needed to spend setting up on every different film.

So, between the technical demands of synchronous audio and pressure from theatre operators to standardize, a coalition of Hollywood studios agreed on a new standard of twenty four frames per second, a standard that has now persisted for over ninety years.

Incidentally, while the Vitaphone sound-on-disc system was the initial forerunner in sync sound, The Jazz Singer was a Vitaphone picture, sound-on-film would eventually win out once the technology for writing and reading the soundtrack improved. Despite the increased complexity of printing the sound to the film, having the sound and picture unified in a single film strip wound up being a far more elegant and robust solution. The Vitaphone discs wore out quickly, they were one more thing to manufacture and ship, and if anything went wrong on either side of the system it was possible for the sound and picture to fall irrecoverably out of sync.