180 Degree Rule (for filming)

The shutter on your camera is the actual thing that goes click when you hit the button. When you click a shot, the shutter opens, exposing the sensor to the scene in front of you.

Your framerate is the number of times the shutter opens in a second, so if you see “Framerate = 24”, it means the shutter is opening 24 times per second (eg you record and play 24 individual frames for every second of video).

Your shutterspeed is the amount of time the shutter is open (letting in light) for a single frame of your video (or for a single photo)–measured in fractions of a second, so if you see “Shutterspeed = 1/200” it means your shutter was open for 1/200th of a second.

Each frame/photo is not actually a “frozen moment in time” as we often call photos; it is all of the light that hit your sensor over the course of 1/200th of a second.

So there will naturally be a difference in the photo/frame when you open the shutter for 1/200th of a second vs 1/50th of a second.

1/200th of a second and 1/50th of a second might both seem like similar amounts of time on a human timescale, but 1/200th of a second is actually 4x as long as 1/50th of a second.

That means that when you’re shutterspeed is 1/50 vs 1/200, it is letting in 4x as much light and capturing 4x as much movement.

The human eye stays open all the time (no shutterspeed), and adjusts automatically (pupils dilate). We naturally and almost universally perceive motion in the same way.

There is no camera that can perfectly replicate this, but video gets closest when the denominator (bottom number) of your shutter speed is ~2x your framerate.

A very common framerate/shutterspeed for highend video is 24 FPS (framerate) coupled with 1/50th Shutterspeed.