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Understanding the Difference in Global and Rolling Shutters

When getting started on video, you may run into a common problem, with no easy explanation of what’s going on. During quick pans, your footage may look like jello, or when recording video of rotating objects, they may look like they’re rotating slower than they are, or not at all. These are all common problems with a rolling shutter, so let’s talk about the differences between a rolling shutter and a global shutter.

At a fundamental level, digital camera sensors are composed of millions of individual photosites that each sends exposure information to the camera’s processor 24, 30, or even hundreds of times per second. The processor takes that information and records it as a video file. Most camera processors aren’t fast enough to handle all of this information at once, so the majority of digital cameras have to expose photosites one row at a time. This is called a rolling shutter.

While every row of photosites is exposed for the same amount of time, they’re not all exposed at once. They transmit information to the processor row by row, top to bottom. Under normal shooting circumstances, this effect is unnoticeable. Sometimes, though, especially when shooting something moving at high speed, it can lead to issues with the image. The most common problem is vertical lines in motion appearing slanted or wavy. This video does a really great job of visualizing how a rolling shutter works and giving examples of the kinds of effects it can have on recorded video.

 

There is no universal look that applies to all cameras and rolling shutters. Some cameras have more effect; some have less. DSLRs with video functionality are typically a lot worse about it than cameras designed specifically for video. But sensor size, processing speed, and framerate can all have different effects when using a rolling shutter.

By contrast, a camera with a global shutter exposes every photosite at once, eliminating the negative image artifacts that a rolling shutter can sometimes cause. However, since a global shutter can sometimes make photosites less efficient, there may be trade-offs in dynamic range and low light performance. Since it also requires significantly more processing power, cameras with a global shutter also typically have fewer high frame rate options. The global shutter version of the Canon C700, for example, has two fewer stops of dynamic range and a top frame rate of 60 frames per second below the top frame rate of the standard Canon C700.

Simulation comparing rolling shutter vs. global shutter

 
Again, rolling shutter, as long as you’re using a video-specific camera under typical shooting conditions, will normally go unnoticed. Given the possible downsides (including cost) of working with a global shutter, I generally steer people away from them unless they have a specific reason in mind. “I need a global shutter because I’m filming airplane propellors at high shutter speeds” is a different request from “I want a global shutter because I’m shooting my first movie, and I heard it’s better.”
 
 

 
So, in short,  if you’re not sure if you need a global shutter, you probably don’t. The effects of one over the other are pretty mild in comparison and will likely be unnoticed unless you’re shooting something at rapid speeds. As the video shows above, the jello effect often associated with rolling shutters is minimal on modern camera systems like Panasonic GH5. While DSLRs will show the effects more prevalently, cameras have come a long way to prevent the side effects of the rolling shutter effect. Regardless, here is a shortlist of our most popular video cameras with rolling shutters and the most common video cameras featuring global shutters —

 

Popular Rolling Shutters Popular Global Shutters
Panasonic GH5 Sony F55
Blackmagic Pocket Cinema Camera 6K Canon EOS C700 GS PL Cinema Camera
Sony a7s III Blackmagic URSA Mini Pro 12K
Canon C200 VRI Phantom VEO4K
ARRI Alexa Mini Blackmagic 4K Production Camera
 Sony FS7 Mark II RED Komodo
 
 

Author: Lensrentals

Articles written by the entire editorial and technical staff at LensRentals.com. These articles are for when there is more than one author for the entire post, and are written as a community effort.

Posted in Geek Articles
  • The thing I have never quite understood when it comes to the rolling shutter effect is why a mechanical shutter eliminates it.

  • asad137

    Yes, the “wagon wheel” effect is an example of aliasing.

  • KeithB

    A motion picture is a form of sampling, so aliasing is as good a description as any.

  • Stanislaw Zolczynski

    Aliasing? It has to do with with frame rate and rotation speed. You can see this effect in many westerns shot on film where carriage spoke wheels seem to rotate backwards.

  • asad137

    Yes, that’s right. The fan blades appearing to rotate backwards at some speeds has nothing to do with rolling shutter and is an example of aliasing.

  • The_Incomparable_Douche

    In the fan test, I couldn’t see much difference between the two cameras.

    If the appearance of the fan blades’ coming to a stop is what is being demoed, wouldn’t that happen whenever the rotational frequency of the blades approaches an exact multiple of the frame rate—regardless of rolling vs global shutter?

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