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What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained

What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained

To capture an image there is one thing you absolutely need. Light. 
But, light is not the only thing the shutter affects. It also plays a big role in how motion is captured. And not all motion looks the same. So, how does an image-maker use the shutter to control light and motion?


What is shutter speed and how does it work?


What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained

Along with aperture and ISO shutter speed is part of the exposure triangle. To understand this, let's recap how a camera captures light. Light enters the lens and it passes through the aperture and lands on the film stock or digital sensor to create an image. In between the lens of the sensor, is a barrier known as the shutter.

What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained

The shutter's job is to block light from the sensor. The shutter opens for a predetermined amount of time before shutting. This repeats many times per second. The amount of time the shutter is open is known as the shutter speed which is usually measured in fractions of a second. For example, a shutter speed of 1/50th lets in light for 1/50th of one second.

What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained



Exposure & Motion Blur


There are two direct effects of shutter speed are exposure and motion blur.

Exposure

The shutter controls how long the frame is exposed to light. The slower the shutter, the longer the frame is exposed to light resulting in a brighter image. The faster the shutter, the less light reaches the frame. resulting in a darker image. 

So let's focus primarily on the different visual effects of shutter speed.

Now, the function of shutter speed in the exposure process is straightforward. But how it affects motion is a little more complicated.

What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained

Every motion picture contains some level of motion blur. Faster shutter speeds reduce motion blur while slower shutter speeds increase motion blur.

What is Shutter Speed: Camera Shutter and the Exposure Triangle Explained



180 Degree Shutter Rule

The most cinematic shutter speed for film and video is found using the 180-degree shutter rule. 180-degree shutter rule says, (The shutter speed should be double your frame rate.) So, if you're shooting 24 frames per second then your shutter speed should be set to 1/48th, and so on.


But why this ratio?

For most of cinematic history, starting in the late 1920s, the industry standard for the film has been 24 frames per second with the shutter angle at 180 degrees. This remained unchanged for decades. Over time we have become accustomed to this amount of motion blur. It's just what movies are supposed to look like terrible.


Deviating from 180 Rule

It's only when filmmakers deviate from this 180-degree shutter rule that we even notice the motion blur. So, let's take a look at how and why cinematographers use various shutter speeds for different effects.

Slow Shutter Speeds

Starting with slow shutter speeds anything set above 180 degrees. A slow shutter creates more motion blur. Which has unique storytelling effects. For example, through a traumatic flashback.

In The Usual Suspects, cinematographer Newton Thomas Siegel shot this scene at 6 frames per second and a wide-open shutter. When played back at 24 frames per second, we see this motion as stuttering with a lot of smearing from the open shutter

Director of photography Rodrigo Prieto used a 360-degree shutter angle at 12 frames per second to increase the motion blur of the image. However, if you're shooting at higher frame rates the 180-degree shutter rule applies less. The Hobbit was shot at 48 frames per second, but it needed a 270-degree shutter to compensate for more natural motion blur.

Another reason to use a slow shutter speed is for long exposure shots. We've been talking about shutter speed in fractions of a second but long exposures can last for minutes at a time. 

"Picasso" actually experimented with what are called light drawings. By using a small light and a slow shutter. Slower shutter speeds can be a creative way to capture highly stylized shots.


Fast Shutter Speeds

On the opposite end, eliminating motion blur has its own unique applications. This is done with a fast shutter speed anything below 180-degrees. A faster shutter speed reduces the amount of motion blur making the video appear jittery or hyper-realistic.

Cinematographers use fast shutter speed stylistically to amplify intensity or realism. This is commonly used in scenes with a lot of action. Often coupled with a handheld camera. Janusz Kaminski famed cinematographer of "Saving Private Ryan" refers to this effect as staccato. Kaminsky shot these sequences with either a 45 or 90-degree shutter.

This extreme lack of blur means we can see individual dirt particles in the air. Creating a frenzied and chaotic visual experience. Kaminsky also used the shutter to a different effect.

By offsetting the timing of the shutter so that light hits the frame while it's moving he was able to create these vertical streaking highlights. A technique he borrowed from "Full Metal Jacket". And used again in "Minority Report".


Last words

As we've discussed, there are certain filmmaking rules when it comes to using shutter speed to create a cinematic look. However, some of the best cinematographers break those rules to create something new. Mastering shutter speed and the exposure triangle as a whole will give you the tools necessary to best tell your story. What other shutter speed techniques are there? Share your favorites in the comments.

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