In 2012, “The Hobbit: An Unexpected Journey” came to cinemas and sparked a controversy. Is it because director Peter Jackson had found a way to turn a short book into a three-film epic, of which this was only the first part? Actually, it wasn’t just that. Instead, Jackson took an unexpected journey himself: He decided to film the Hobbit at 48 frames per second (fps), rather than the usual 24 fps used by almost every other film in existence. His choice of frame rate portrayed motion in a smoother but very different way than most viewers were used to.
In fact, a video’s frame rate profoundly affects how people perceive and react to it. And 24 fps and 48 fps aren’t the only possible frame rates. Many television broadcasts use 25 fps or 30 fps, while other specialized programs like sports often use 60 fps.
With all these frame rates, which one should you use while filming a video, and while outputting it? Should you stick to the standard or try something experimental like Jackson? Let us take a look at everything from tradition to the bleeding edge to answer this very tricky, and sometimes contentious, question.
|Frame Rate||Recommended 180° Shutter Speed||Typical Usage|
|24 fps||1/48||Feature Films|
|25 fps||1/50||European Television|
|30 fps||1/60||North American Television|
|48 fps||1/96||Some films, e.g. The Hobbit|
|60 fps||1/120||Sports broadcast, wildlife|
|120 fps||1/240||Gemini Man|
Table of Contents
A Tale of Strange Frame Rates
Most modern cameras happily churn out a variety of frame rates like 24 fps, 30 fps, 50 fps, 60 fps, and 120 fps. However, chances are when you set your camera to 24 fps, it’s actually shooting a hair under 24 frames each second – usually 23.976 fps instead. Similar, bizarre-looking numbers also occur with other frame rates, although some cameras can shoot in true 24 fps, like the Panasonic GH6.
The differences between the nice round numbers and those with decimals involve the technicalities of broadcast and distribution. These differences are not really important here since we are discussing how frame rates affect the appearance of your video. So, from that perspective, I will simply use nice whole numbers like 24 fps.
Also, for most of this article, I will be talking only about the output frame rate, or the frame rate of the final product. It still makes sense to shoot at higher frame rates than your output frame rate for the purposes of slow motion, which I will briefly mention later on.
How Frame Rates Affect Our Perception of a Video
The higher the frame rate (i.e. the more frames per second), the smoother the depiction of motion. Can us mere mortals notice this difference? Indeed we can.
Let’s look at 24 fps, 30 fps, and 60 fps clips of a Mallard duck happily drinking water. (I both filmed and played back the video at those frame rates.) My shutter speed for each clip was the closest available setting to the 180 degree shutter rule, so 1/50, 1/60, and 1/125 respectively. Note that YouTube defaults to playback at 30 fps for some users, so you may have to select 4k60 on the third clip’s video settings in order to watch it properly:
We can see that the 25% increase from 24 fps to 30 fps already makes a huge difference. This is typically more noticeable with quicker motions like those of birds compared to the smoother motions of humans, which is one reason why I think 24 fps is a poor choice for filming and playback of wildlife videos. The difference between 30 fps and 60 fps is also pretty big, with 60 fps giving even more smoothness that many people are not used to.
Best Shutter Speed for Different Frame Rates
How does shutter speed fit into the equation? Shutter speed affects our perception of detail, and different frame rates are supposed to use different shutter speeds for the most natural-feeling results. The standard rule is that the shutter speed should be “one over twice the frame rate.” For example, 1/48 shutter speed for 24 fps video. This is the 180 degree shutter rule I mentioned earlier, and it gives a good feeling of motion at the chosen frame rate.
Of course, other speeds can be used for creative effect. One such deviation from this rule is the faster shutter speed used for a chaotic effect, like in the war film Saving Private Ryan. One could also use slower shutter speeds such as 1/24 for 24 fps, which gives a dreamier, smoother effect.
If you follow the 180 degree rule, the result is that different frame rates will have different levels of detail. For instance, consider these frames extracted from videos taken at different frame rates, all of which use the 180 degree shutter rule:
Because I dropped the soccer ball from the same height every time and took the frame from about the same position in each video, the laws of gravity imply that the ball was traveling at the same speed in each of these shots. Interestingly, the nature of the ball being a patchwork of pentagons and hexagons only becomes fairly clear at 60 fps and 120 fps, whereas at lower frame rates, the spherical essence of the ball is all that we can perceive.
These differences are particularly relevant for illustrating motion. One film research group looking at dancing remarked that “imperfect movements, whether a shaky moving shot or jerky dance move, became even more pronounced” with higher frame rate video. Thus, lower frame rates such as 24fps may serve to enhance a viewer’s ability to suspend disbelief and only see the essential details.
Which Frame Rates Do People Prefer?
As we can see, higher frame rates give more detail and smoother motion. Is smoother motion always better? One study showed clips from fiction films at 24 fps and 60 fps and found some people could not distinguish between the two frame rates – but those who could preferred 24 fps.
Many people also describe 24 fps has having a magical cinematic quality, whereas higher frame rates are looked upon with suspicion. Odie Henderson’s review of Gemini Man described the effect of the film’s 120 fps as “a hellish cross between a video game and a telenovela,” which is not really something I’d like to hear about one of my films.
So at least for fictional movies, 24 fps is not only safe but entrenched. The general negative impression of The Hobbit’s 48 fps choice only served to make 24 fps more popular. Therefore, it would be hard to go wrong with 24 fps if you’re making your own movie or something for film school. And although as a wildlife photographer, I avoid 24 fps (more on that later), I’m pretty sure I’d still use 24 fps if someone asked me to direct the next James Bond.
Still, is 24 fps the last word? Not necessarily. Another group from the University of British Columbia did a careful experiment where they captured and showed to viewers footage at 24 fps, 30 fps, 48 fps, and 60 fps. However, this time the footage was captured and shown in 3D. They found that people overwhelmingly preferred higher frame rates, with 60 fps being rated as the best.
The preference for higher frame rates is not restricted to 3D content. A group at the University of Bristol looked at a variety of video clips and asked users to rate their quality. These videos were random scenes like people riding bicycles, and not clips taken from feature films. In this case, there was a strong preference for higher frame rates. Therefore, it appears that outside of fiction, there is less support for the venerable 24 fps. I filmed the water below at 60 fps, and playback is at the same speed if YouTube supports it for you:
So, What Frame Rate Should You Use?
For choosing frame rates, we have seen that context and format clearly matter. In fictional cinema, there is no doubt that 24 fps – the “vanilla” of filmmaking – still reigns supreme. Because 24 fps is ubiquitous, and because its lack of detail may also aid in immersing viewers in a fictional world, it is hard to argue against 24 fps in this case.
For wildlife videos, higher frame rates are closer to reality. That’s definitely a benefit if you’re aiming for realism, rather than for suspending the audience’s disbelief. Animals such as birds and insects also move much more quickly and jerkily than humans, and so the choppiness of 24 fps is more apparent with them. Plus, animals sometimes have quick behaviors may not be visible at 24 fps.
For these reasons, I prefer 60 fps for wildlife video, both for filming and playback. However, I have found that 30 fps is still a pretty good choice, since it removes much of the apparent choppiness.
Another important consideration is filming slow motion. Slow motion video is done by filming at high frame rates like 120 fps and playing back at 30 fps (without dropping frames). If you use 30 fps playback, you can shoot at 60 fps or 120 fps for slow motion. Whereas if you use 60 fps playback, you need to make sure that your camera can shoot 120 fps (or higher) if you want slow motion.
For other types of videos like documentary or instructional, the choice is less clear. From their experiments, the high frame rate research group at the Emily Carr University believes that in some cases, the increased realism of higher frame rates provides more intimacy with the characters on screen. This could be good or bad depending on your requirements.
In all cases, I also can’t stress the creative aspect enough. Despite the complexities surrounding frame rates, what looks good – and serves the needs of your project – should still be at the forefront of your mind. Therefore, I also suggest experimentation, especially if you are producing content outside the mainstream.
For Slow Motion
So far, I have mostly talked about the output frame rate (the one that looks best in your final clip). But even if you want to display your video at 24 fps, it still makes sense to consider shooting at other frame rates for slow motion. For example, if you shoot at 120 fps, you can slow that down to 24 fps to get 5x slow motion. Here is an example of 6x slow motion shot at 180 fps, slowed down to 30 fps:
Which frame rate should you use for slow motion? The answer is the slowest one that allows you to display what you want. People move fairly slowly and smoothly, so 60 fps is usually enough for videos of people.
On the other hand, birds and small animals move more quickly. I find that 120 fps or 180 fps is good to show flying birds, although even higher frame rates like 300 fps look good for very small birds. If you really need to slow down motion, Kron Technologies makes a specialized camera that can shoot at 1000 fps, and yet is relatively affordable compared to most slow motion cameras.
You might just be tempted to shoot at the highest frame rate possible and then choose the level of slow motion later. It’s not necessarily a bad approach, but before you do that by default, consider the following example. I took my Panasonic G9 and shot two videos of a nonmoving subject: one at 30 fps and one at 180 fps. I used the same ISO and aperture, but of course different shutter speeds. To compensate for the different shutter speeds, I carefully turned up my video light until a proper exposure was obtained in both. Note that the level of detail is better in the 30 fps shot:
It’s clear that the quality with 180 fps looks more compressed. That’s because higher frame rate video like 180 fps often has reduced quality on many cameras, so you should not go higher than necessary when maximum quality is important to your shot.
Finally, I should mention that the 180 degree shutter rule says to shoot at one over twice the frame rate at which you are shooting, even if the final output frame rate is different. For example, if you your final video will be in 30 fps, but you are shooting at 60 fps for a 2x slow motion effect, you should shoot at 1/125 while you are shooting at 60 fps.
We have seen that there are some established standard frame rates, but the frame rate you choose should also be based on your content and your creative direction. The lowly 24 fps is still overwhelmingly used for cinema, whereas higher frame rates like 30 fps, 50 fps, and 60 fps are becoming more popular with 3D content and are good for wildlife videos.
With these points in mind, I am confident you will choose the frame rate that’s best for you. If you have any ideas about choosing frame rates, I would be happy to discuss them in the comments.