Remember those little flip books where a stack of paper had an image on every page, and when you flipped through the pages quickly, the image would appear to animate and move?
This is the same way Video works.
Frame rate is the speed at which those images are shown, or how fast you “flip” through the book and it’s usually expressed as “frames per second,” or FPS. Each image represents a frame, so if a video is captured and played back at 24fps, that implies each second of video shows 24 distinct still images.
Movies are usually displayed at 24fps, since this frame rate is similar to how we see the world, and creates a very cinematic look. Video that’s broadcast live or video with a lot of motion, such as a sporting event or video game recording, will often have a higher frame rate like 60 fps, as there’s a lot happening at once.
But here’s the catch, If I am outputting everything at 24 fps for a cinematic look does it mean I capture everything at 24 fps too?
The answer is No. So here’s my take on how to approach different situations with different frame rates.
When you want your footage to play at the original pace, Shoot at 24 fps.
Or if you want to slow down or speed up your footage, Shoot at higher frames like 60 fps or 120 fps and so on. This is how people capture buttery smooth visuals by capturing a video at a higher frame rate and converting it to a lower frame rate while editing.
So let’s say that I have captured a video at 120 fps. In post I’ll be converting it to 24 fps as its the standard output frame rate to give videos a cinematic look.
When you convert, 120 frames in one second becomes 5 seconds of 24 fps footage.
The Chapati Dough Analogy
I have always related Cooking with Videography since it has a lot of similarities which we’ll discuss later but for now let us focus on rolling the chapati dough. When you are rolling the chapati dough, there’s a certain threshold to how thin you can roll it, right? Beyond that, the Chapati will start breaking.
Similarly, when you are slowing down the footage, there’s a threshold to how much you can slow it down. And this can be simply calculated by the following formula.
Slow Motion threshold percentage % = Frame rate(shot at) / Frame rate(output) * 100
For this example, we shot the footage at 120 fps and we are outputting it at 24 fps, so the threshold percentage will be 120/24=5, 5*100=500. So you can slow down the footage upto 500 percentage without resulting in jittery footage. That was my chapati analogy and hope you found it interesting. We will dive deeper into frame rates and things like the 180 shutter rule in the next article.
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