Have you heard the terms rolling shutter and global shutter and have no idea what they mean?
Are you curious about the inner workings of your camera’s shutter mechanism? Do you ever wonder why some photographs appear distorted or skewed while others capture motion with crystal-clear precision?
The answer lies in the battle between two shutter technologies: the rolling shutter and the global shutter.
In this article, I’ll delve into the fundamental differences between these two systems, shedding light on how they operate and their impact on your photography.
Whether you’re a professional photographer or an enthusiastic hobbyist, understanding rolling shutter’s and global shutter’s nuances will empower you to make informed decisions when capturing those perfect moments.
Let’s dive in!
What is the Difference Between Rolling Shutter and Global Shutter?
In short, the main difference between a rolling shutter and a global shutter is how they capture images.
A rolling shutter scans the scene sequentially, line by line, or column by column, resulting in potential distortions and artifacts for fast-moving subjects.
A global shutter captures the entire frame simultaneously, freezing the motion at a specific point in time, ensuring an accurate representation of moving objects without distortion.
The choice between the two depends on factors such as desired image quality, motion accuracy, and low-light performance.
To further grasp the disparities between the two, let’s take a look at the specifics:
1. How They Operate
The rolling shutter operates by exposing different parts of the image sensor sequentially.
It scans the scene from top to bottom or left to right, capturing one line or column of pixels at a time.
This scanning process creates a rolling effect when capturing fast-moving subjects or when the camera itself is in motion.
On the other hand, the global shutter exposes the entire image sensor simultaneously — capturing the entire frame in one go, freezing the motion at a specific point in time.
This synchronous exposure ensures that all parts of the image are captured simultaneously, avoiding any distortion caused by movement during the exposure.
2. Motion Artifacts
Another key distinctions between rolling shutter and global shutter is the presence of motion artifacts.
Due to the sequential scanning nature of the rolling shutter, fast-moving objects can appear distorted or skewed in the final image.
This effect is commonly referred to as the “jello effect” or “rolling shutter distortion.”
Here’s an example of how each shutter would capture a fan:
Here’s a great example explained by SmarterEveryDay
It occurs when objects move significantly during the scanning process, resulting in non-uniform representation across the image.
In contrast, the global shutter eliminates rolling shutter artifacts by capturing the entire frame simultaneously.
It freezes the motion at a particular moment, ensuring that moving subjects are represented accurately without any distortions caused by the scanning process.
3. Camera Sensor
Rolling shutter is the most commonly used mechanism in CMOS sensors, which are the sensors commonly found in digital cameras, smartphones, action cameras, camcorders, and surveillance cameras.
Global shutter is most commonly used in CCD sensors which aren’t as popular as they used to be.
So you might be thinking that a rolling shutter is used in most modern-day cameras — you will be correct.
Rolling shutter provides us with a better resolution and higher frame rates, and the distortions you can receive with a rolling shutter are a small price to pay.
Speaking of rolling shutter, let’s take a closer look at what it means along with a global shutter.
What is Rolling Shutter?
Rolling shutter is a method of capturing images in which the camera’s sensor scans the scene sequentially, line by line or column by column, during the exposure process.
Instead of exposing the entire frame at once, the sensor captures different parts of the image at slightly different times.
This scanning technique introduces a potential distortion effect known as the rolling shutter effect.
When using a rolling shutter, the exposure starts at one edge of the frame and progresses to the other edge.
This sequential scanning creates a time disparity between the capture of the top and bottom or left and right portions of the image.
Consequently, if there is any movement or motion occurring during the exposure, it can lead to visual artifacts and distortions in the final image.
For example, let’s say you’re photographing a sporting event. As you press the shutter button, the exposure will begin at one edge of the frame and move across to the other edge.
So let’s say a soccer player kicks the ball. Due to the sequential scanning, the top part of the image may be captured slightly earlier than the bottom part which could result in the player’s legs or the ball appearing distorted or skewed.
Advantages of Rolling Shutter
Now let’s take a look at the advantages of using a camera with a rolling shutter:
1. Higher Frame Rates
The first advantage is with higher frame rates.
Rolling shutter allows cameras to achieve higher frame rates compared to global shutter.
By sequentially scanning the image sensor, each line or column can be read out at a faster rate, enabling cameras to capture more frames per second.
This makes rolling shutter advantageous in applications that require smooth motion capture, such as sports photography or fast-action videography.
2. Power Efficiency
The second advantage is with power efficiency.
Rolling shutter technology tends to be more power-efficient compared to global shutter.
Since the sensor reads out data sequentially, it can activate and deactivate specific sections of the sensor as needed.
This selective activation helps conserve power, making rolling shutter suitable for devices with limited battery life, such as smartphones and portable cameras.
This is important because with our reliance on technology these days (such as our smartphones), battery life and power efficiency are important to us.
The third advantage is with cost-effectiveness.
Implementing rolling shutter in camera systems is generally more cost-effective compared to global shutter.
Rolling shutter sensors are typically less complex and require fewer components than their global shutter counterparts.
This cost advantage contributes to the widespread adoption of rolling shutter in consumer-grade cameras and entry-level professional cameras.
This is why I mentioned earlier that CCD sensors which often used global shutters aren’t as popular anymore.
4. Higher Dynamic Range (HDR)
The fourth advantage of rolling shutter is how they handle dynamic range.
Rolling shutter sensors can handle high dynamic range (HDR) scenes effectively.
By scanning the scene sequentially, they can adapt to different light intensities across the frame.
This adaptability enables rolling shutter cameras to capture a wide range of brightness levels, preserving details in both shadowed and well-lit areas.
Disadvantages of Rolling Shutter
We looked at the advantages of a rolling shutter, now let’s take a look at the disadvantages.
I’ve already mentioned one of them earlier but let’s take a closer look at each one:
1. Distortion With Moving Subjects
The first disadvantage of a rolling shutter is with the distortion of moving subjects.
As the exposure progresses sequentially across the frame, any movement that occurs during this time can lead to visual artifacts and distortions.
Moving objects, such as a rotating propeller or a fast-moving vehicle, may appear warped or skewed in the final image or video, causing the so-called “jello effect” or “rolling shutter effect.”
2. Reduced Motion Accuracy
The second disadvantage of a rolling shutter is with reduced motion accuracy.
In scenes with rapid motion or quick changes in direction, the captured frames may not accurately represent the precise timing or positioning of moving subjects.
This can lead to a loss of detail and a lack of sharpness, particularly when capturing subjects with high-speed movements.
3. Challenging Vertical Movements
The third disadvantage comes with challenging vertical movements.
What I mean by this is that a rolling shutter is particularly susceptible to vertical movements of the camera.
When panning vertically or tilting the camera, the scanning direction becomes more noticeable, leading to skewed vertical lines in the image.
This effect is commonly referred to as the “leaning tower” or “vertical skew” and can be visually distracting, especially when capturing architectural or straight-line subjects.
4. Limited Flash Sync Speed
The fourth disadvantage comes with limitations when synchronizing with external flashes or strobes, limiting flash sync speed.
Since the exposure occurs sequentially, the flash may not synchronize perfectly with each line or column scan, resulting in partial illumination or uneven lighting across the frame.
This can be a concern in situations where precise and consistent flash synchronization is crucial, such as studio photography or capturing fast-moving subjects with flash.
Now that we’ve explained everything there is to know about rolling shutter, let’s take a closer look at the global shutters.
What is Global Shutter?
Global shutter captures the entire image at once, freezing all the pixels simultaneously.
When using a global shutter, each pixel’s charge is captured and stored during the exposure period, ensuring that all parts of the image have the same exposure time.
This simultaneous exposure eliminates the potential distortion and artifacts that can occur with rolling shutter, especially when capturing fast-moving subjects or during camera motion.
Advantages of Global Shutter
A global shutter offers several advantages in comparison to a rolling shutter:
1. Elimination of Rolling Shutter Artifacts
The first and most obvious advantage of a global shutter is the elimination of rolling shutter artifacts.
As mentioned in the previous paragraphs, with a global shutter, the entire frame is exposed simultaneously, ensuring that all pixels capture the same moment in time.
This eliminates distortions and visual artifacts that can occur with a rolling shutter, particularly when capturing fast-moving subjects or during camera motion.
A global shutter ensures an accurate representation of motion and prevents the “jello effect” or skewed objects in the final image or video.
2. Accurate Representation of Fast-Moving Subjects
The second advantage of using a camera with a global shutter is the ability to capture fast-paced action with precision.
Since the exposure is simultaneous across the entire frame, there is no time disparity between the capture of different parts of the image.
This enables global shutter cameras to accurately freeze the motion of subjects, maintaining sharpness and detail even in high-speed scenarios.
It is particularly advantageous in applications such as sports photography, wildlife photography, or any situation where capturing fast-moving subjects is crucial.
3. Simplicity in Flash Photography
The third advantage of a global shutter is the simplification of flash photography.
Global shutter simplifies flash photography by allowing for precise synchronization with external flashes or strobes.
Since the entire frame is exposed simultaneously, there is no need to worry about partial illumination or uneven lighting caused by asynchronous flash timing.
This makes global shutter ideal for studio photography, portrait photography, or any scenario where accurate and consistent flash synchronization is essential.
4. Versatility in Light Sources
The fourth advantage of a global shutter is it’s versatility in light sources.
Global shutter handles scenes with flickering lights or electronic displays more effectively than rolling shutter.
With simultaneous exposure, it captures each frame consistently, avoiding banding artifacts that can occur when capturing flickering light sources with rolling shutter.
This makes global shutter suitable for applications like concert photography, event coverage, or any situation involving varying light sources.
This is one of the reasons why many Hollywood cinematographers opt for cameras with global shutters.
Disadvantages of Global Shutter
We’ve covered the advantages of a global shutter, now let’s take a look at some of the disadvantages.
You’ll find that many of these are the opposites of the advantages of a rolling shutter that I wrote about earlier:
1. Reduced Frame Rates
The first disadvantage of a global shutter is the reduced frame rates.
Since the entire frame is exposed simultaneously, it requires more time to read out and process all the pixels.
This can limit the maximum achievable frame rate.
2. Increased Power Consumption
The second disadvantage of a global shutter is the increased power consumption.
The design of global shutter sensors often requires more power consumption and generates more heat compared to a rolling shutter.
Capturing the entire frame simultaneously necessitates more complex circuitry and increased data throughput, which can result in higher power requirements and potential heat dissipation challenges.
This can impact battery life and may require additional cooling mechanisms, particularly in continuous shooting situations or when operating in high-temperature environments.
4. Reduced Dynamic Range
The fourth disadvantage of a global shutter is the reduced dynamic range.
The simultaneous exposure of all pixels may result in overexposure of bright areas and underexposure of dark areas in high-contrast scenes.
This can lead to loss of detail in highlights and shadows, limiting the sensor’s ability to capture the full range of tonal values in a scene.
Conclusion: Rolling Shutter vs Global Shutter
In a perfect scenario, every camera would be equipped with global shutters, allowing all pixels to be switched on and off simultaneously. This would eliminate the distortion associated with rolling shutter mode.
But there are advantages and disadvantages to both. Determining which advantages are important to you is the important part.
Frequently Asked Questions
Is rolling shutter same as global reset?
No, rolling shutter and global reset are not the same; rolling shutter refers to the sequential scanning of an image sensor, while global reset is a method used to reset the sensor’s pixels simultaneously.
Why is global shutter more expensive?
Global shutter tends to be more expensive due to the additional complexity and specialized components required for simultaneous exposure of all pixels, increasing production costs.
Do mirrorless cameras have rolling shutter?
Yes, mirrorless cameras can have rolling shutter, as the scanning method is determined by the type of image sensor used rather than the presence or absence of a mirror mechanism.
Nate Torres is an entrepreneur, growth marketer, and photographer and writes mostly on those topics. Nate runs his own professional photography business and photography blog called Nate Torres Photography. Nate enjoys learning about new digital marketing strategy and new ways to think creatively. He is also a photography speaker and author on Photofocus.