eli5 : Is 1000 fps is always slow motion?

35 views

Can you play a video in 1000fps at normal speed?
Or play a game at normal speed with this fps?

In: 0

1000fps refers to how many frames were captured in a second. It’s then played at a typical fps that we can actually watch and understand.

How fast we can display fps is limited by our hardware. How fast can the monitor show a new frame? How fast can these images be processed?

Typically if you’re recording that fast, it’s so you can watch something slowed down.

The human brain/eye only processes about 16fps (but because we aren’t perfectly synced with whatever video we’re watching, we can tell the difference). 120fps is about the max of what our brains need for it to be seamless without it becoming superfluous.

So yes, currently high speed cameras are used for slow motion because anything beyond 120fps is excessive for the average person.

Slow-motion (or fast-forward) happens if you display the video at a different frame rate than it was shot at.

If you shoot at 24fps and show the video at 24fps, you’re getting a normal video. If you instead slow down the playback to show the video at 1fps, it takes 24 seconds to show a clip that took one second to record, resulting in an extremely choppy slide show.

If you pump up those numbers and shoot at 240fps but show the result at 24fps, you get a comparatively smooth video that still stretches one second of footage into 24 seconds of view time which lets you see details you’d otherwise miss.

Technically speaking there’s nothing stopping you from shooting and displaying video at 1000fps, but it’s pretty tough to find a monitor that can show images that fast, especially when at some point you stop seeing the difference.

A video is slowed down by replaying it at a lower FPS. If you could display 1000fps then it would be normal speed.

60 fps would be slow motion if you played it back at 1 fps, but then it’d be a slideshow. 1000 fps would be used so you could replay it at a lower fps but still see motion because it’s still a reasonable viewing fps.

Edited for clarity, hopefully.

At the moment, yes. But that’s only because we can’t play anything back at 1000fps. (As far as I know)

Slow motion is quite simply when you record something at a higher rate than you play it back. So if you record it at 1000fps and pay it back at 500fps, then it will appear to be slow motion.

It would be a massive waste of time and money to play a 1000fps video at normal speed. It costs a lot of money to generate a video with that many frames per second. When you playback that video on a normal TV or monitor that only displays 60fps, 940 of those frames are wasted each second.

The purpose of the higher frame rates for recording is so that the clip can be stretched out without losing smoothness.

Take 60fps as the benchmark for smooth viewing (think video game standard). If I record at 60fps but play it back at 25%, it runs at 15fps, which is a very choppy playback. If I record at a lower frame rate, like 25fps, and slow it down to 25%, it runs at 6fps, which is horrible. Think gas station security cameras replayed in slow motion where the culprit teleporting from the door to the counter.

So if I want something resembling the same smoothness as 60fps real time, I need to record in a higher frame rate. My Gopro records at 240fps. I can slow the footage down to 25% speed and get the same smoothness as a real time video in 60fps.

But let’s say that 25% speed is still too fast. I might want ti capture an arrow in flight, and it’s moving too fast to see even in slow motion. I could render it at 12% speed and still have an acceptable smoothness. But even that might be too fast. If I want to capture the majestic flight or the impact, I might need 5% speed. To get the smoothness at 60fps high definition, I need to record in 1200fps.

And that’s where your question comes in.

You only record in high FPS if you intend to use it for slow motion. If I don’t plan on it, I record in 60fps to play at normal speed. Recording at higher frame rate requires more powerful recording tech and much larger file sizes than what is needed for normal playback.

In short, 1000fps isn’t slo mo. It’s recorded in 1000fps so that the video can be slowed down without losing frames that we can see.