Smooth movies: Are high-frame rate films a good idea?

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Ben Rosenstein/Paramount

Every few years Hollywood releases a movie with high-frame rate, or HFR. The most recent, Ang Lee’s Gemini Man, was intended by the director to be seen at 120 frames per second, five times the traditional 24fps. Lee is not alone in his love of HFR. Peter Jackson, of Lord of the Rings and Hobbit fame, thinks HFR is the future of cinema as well. They, and other fans of HFR films, laud the realism and clarity compared to traditional 24fps.

Detractors, for their part, claim HFR prevents the suspension of disbelief that’s so important in fictional cinema. They say shooting in high-frame rate makes movies look more like camcorder footage, reality TV or a soap opera, never elevating the image above actors on a cheap set.

Recently I had an illuminating conversation on Twitter — yes, it’s possible — where several HFR fans pleaded their case. I argued that for most people, the traditional 24fps of movie and scripted TV shows displays “fiction,” while higher frame rates are typically the realm of “nonfiction,” like sports and amateur video. The difference turns out to be a serious issue, but to explain why, let me first discuss the basics.

What is frame rate?

Frame rate is the number of images per second shown to create a moving picture. If you see a high enough number of still images  in quick succession, your brain combines them into motion. In the case of nearly all modern movies and scripted TV shows, the standard rate is 24 frames per second (fps). Other TV shows and sports, as well as video games, use higher frame rates of 30, 60 or even 120fps.

Twenty-four fps dates back to the early days of movies with sound nearly a century ago. When you only have 24 frames to work with, any fast motion, including on-screen action or simply the camera panning across a landscape, can blur or seem jerky (that is, not smooth). These are the main reasons many HFR proponents push for higher frame rates. HFR is certainly newer, smooths out pans, and greatly improves resolution with fast motion.

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Your TV is a bit different. In the US, most TVs display everything at 60Hz or 120Hz (for this discussion, fps and Hz amount to the same thing). To fit 24 into 60, there’s a process called 3:2 pulldown, which is complex but we’ve it discussed before. In the UK and Australia it’s 50Hz, which does the conversion a bit differently. To make it easier I’m just going to talk about the US numbers, so if your country has 50Hz electricity just read 50 and 100 when I say 60 or 120.

HFR

High frame rate basically means movies and scripted TV at anything greater than 24fps. Examples include The Hobbit’s 48fps and Gemini Man’s 120fps. It’s not a new concept. In the late ’70s, Showscan ran big, expensive 70mm film at 60fps, which I’m sure Kodak would have loved to have become the norm. 

Many new TVs are 120Hz, or at least claim to be. It varies how they create 120 “frames” per second when the original content is 24, but one of the most common is to use some clever processing to create new frames based on the adjacent frames. These TV-created frames are placed in between the originals. This can create the so-called soap opera effect, which we’ll discuss more in a moment.