As you get started with video, you might hear intimidating, super-technical sounding terms like frame rate. But what is frame rate and why does it matter?
The Video is a Lie
At some point in your childhood, you probably came across one of those cool little flip books that showed you how animation worked. Essentially, it was a series of still images (one per page) that, when you flipped the pages quickly, would appear to animate or move. If you haven’t seen one, they look like this:
Pretty cool, eh?
The thing is, that’s essentially how all video works, not just animation. All video, whether digital or old-school film, is simply a series of still images that, when viewed in order at a certain speed, give the appearance of motion.
Frame rate, then, is the speed at which those images are shown. It’s expressed as “frames per second,” or fps. Each image is a frame. So, if a video is captured and played back at 24 fps (the rate of a typical film shown in a cinema), that means that each second of video shows 24 distinct still images. The speed at which they’re shown tricks your brain into perceiving smooth motion.
Generally, the higher the frame rate, the smoother the video, because there are more images to show the motion of whatever you’re trying to capture.
Oh! So higher frame rate is always better, right?
Well, that’s a little complicated.
A quick Google search shows some controversy and that controversy can be … shall we say … heated. Some research shows that humans process the things we see in the world at around 40 fps. Other research disputes that finding based on many factors, including the idea that in the real world, our vision isn’t based on still images giving the appearance of motion, but is instead a constant stream of real-time information. Hardcore gamers who use extremely high-end computers will tell you that anything less than 60 fps is unacceptable. However, it’s not nearly that simple.
As I mentioned above, most feature films are shot and viewed at 24 fps*. The reason for that is pretty simple: In the early days of filmmaking, that was determined to be the minimum speed you could capture while still maintaining a good sense of motion AND saving money on film. Most would agree that 30 fps is actually better, and you see more videographers using that standard if they’re shooting in digital format.
Today, some filmmakers are experimenting with even higher frame rates, but there has been some pushback. The main problem with using a higher frame rate is that you lose some of the things that make motion seem real, such as motion blur. Some people call this the “soap opera effect.” Even though the video is technically of higher quality, it starts to look unnatural because the blurriness of fast-moving objects is part of how we view things in the real world.
This video does a pretty good job of illustrating the difference between 30 fps and 60 fps. Note: To get the full effect, make sure you click the little gear icon at the bottom of the window and set the quality to 1080p60.
Can’t see the embedded video? Watch 60fps vs 30fps Comparison on YouTube
There’s also the issue of screen refresh rate. Screen refresh rate is very similar to frame rate, in that it’s the rate at which your monitor or TV refreshes or shows a new image. Refresh rate is expressed in hertz (hz). Most consumer-grade computer monitors have a default refresh rate of 60 hz, which means it refreshes (or shows a new image) 60 times per second. So, any value gained by capturing video above 60 fps would likely be lost on those monitors.**
Your HD television is typically better than that. Most HD TVs have a refresh rate of at least 60 hz and many are at 120 hz. Newer Ultra HD (UHD) TVs may have a refresh rate of 240 hz. So, higher-frame-rate video will be able to take advantage of those higher refresh rates. Again, though, you need to be wary of the soap opera effect.
However, there’s also a more practical reason why using the highest frame rate possible isn’t necessarily the always best idea: file size.
Remember, the higher the frame rate, the more still images are packed into each second of video. More images means more information. More information means bigger digital files. In fact, one hour of HD video at 30 fps can be as large as 900 megabytes or more. If you’re planning on saving your video to your hard drive or sharing it with someone who will store it on a local drive, file size can be a big issue.
File size and video quality are also something to consider when uploading your videos to online streaming sites such as YouTube, Vimeo and Screencast.com. Higher quality video is always the most desirable, but remember that videos with larger file sizes will take longer to upload and will require better internet connections and computer hardware to stream at its highest quality.
Ok, then how do I choose the best frame rate?
The short answer is that there is no such thing as the “best frame rate.” What you really want to do is choose the right frame rate for your particular video, taking into account your audience’s needs and where they will view it.
Here are four tips for choosing the right frame rate for your viewers:
- Try to record at 30 fps or higher.
- Avoid capturing or sharing video with frame rates below 24 fps.
- Use a higher frame rate if you’re trying to capture fast-moving objects, animals or people that you intend to show in slow motion.
- Choose an online platform that allows viewers to choose quality of the video they’re viewing, so even those with slower internet connections or computers will be able to watch the video, albeit in lower quality. Services such as YouTube, Vimeo or Screencast.com all have this capability.
If you’d like to play around with frame rates and see a little more about how they work, this site offers some fun ways to experiment.
If you have further questions or just want to offer suggestions, I’d love to hear from you in the comments section below!
*This is for film cinema projectors. Digital projectors may have a different frame rate. Also, film projectors have some other tricks up their sleeves to smooth out the finished product.
**Refresh rate and frame rate are not identical, but for the purposes of this post, we won’t go into the nuts and bolts of what makes them different.
***Technically, the actual frame rate is 29.97 fps (yes, that’s silly. You can blame your television), but if you do 30, you’ll be just fine.