The Difference Between Different Camera Shutters

It used to be so simple. The camera shutter opened and closed again. The time in between was the exposure time. With digital cameras and mirrorless systems, things became a bit more complicated. Let’s have a look at the different types of camera shutters.

The camera shutter has only one task: it has to make sure the right amount of light reaches the sensor. This can be achieved in more ways than one. It used to involve some kind of system that opened and closed again. With the digital era, there are more ways this can be done.

The Mechanical Shutter

There are basically two ways to achieve the exposure time with a mechanical shutter. The first one is the leaf shutter; the second one is the focal plane shutter.

The Leaf Shutter

A leaf shutter is probably the oldest type of shutter. It’s located in the lens, at the same location as the aperture. The shutter opens from the middle towards the outer rim and back. The width of the opening acts as the aperture, and the time it opens is the exposure time. Due to this construction, it’s not possible to reach extremely fast shutter speeds.

A leaf shutter is probably the oldest type of shutter. It’s located in the lens, at the same location as the aperture. The shutter opens from the middle towards the outer rim and back. The width of the opening acts as the aperture, and the time it opens is the exposure time. Due to this construction, it’s not possible to reach extremely fast shutter speeds.

Because it is located in the same spot as the aperture, the leaf shutter is always built into the lens itself. This is the most ideal position for an optical system. It allows flash photography with every available shutter speed. Perhaps more importantly, it isn’t prone to the rolling shutter effect.

For cameras that can exchange lenses, every lens needs a leaf shutter. It makes lenses larger, heavier, and more expensive.

The Focal Plane Shutter

The focal plane shutter is located inside the camera. With this system, lenses are smaller and less expensive. It works with two curtains: one opens, and the second closes afterward. Because of the sensor dimensions, the shortest distance for a shutter curtain to travel is in the vertical direction.

Up until a certain exposure time, the sensor will be exposed to the light completely. When the shutter speed becomes faster, the second curtain starts to close before the first curtain has opened completely. In that case, the opening becomes a small slit that exposes the sensor, starting at the top and ending at the bottom.

When flash is used for exposure, a small slit doesn’t allow the sensor to receive the short flash of light. Only when the sensor is exposed completely will a flash allow proper exposure. The maximum shutter speed that will expose the sensor completely is the flash synchronization time.

Focal plane shutters allow for very fast shutter speeds, up to 1/8,000 second. But if the curtains are too slow, the feared rolling shutter effect will occur. With cameras that have a mirror, every image will have a blackout as well. However, a mirrorless camera also has a blackout because the first curtain has to be closed before the exposure can happen.

The curtains of a focal plane shutter used to be made of fabric. Nowadays, more rigid materials are used, which allow faster moving speeds and thus faster exposure times.

The Electronic Shutter

The electronic shutter has no moving parts anymore. This allows for silent shooting. There are also faster exposure times possible, even up to 1/64,000 seconds or more.

These shutters are limited to mirrorless cameras. There are three types of electronic shutters: the normal electronic shutter, the electronic first curtain, and the global shutter.

Normal Electronic Shutter

With a normal electronic shutter, the reading out of the sensor data is line by line. Although the exposure time can be extremely fast, the readout time is limited to the bandwidth. There is only so much information that can be recorded at once. If the readout isn’t fast enough, the rolling shutter effect occurs, and color shift can be visible.

The benefit is the lack of sound and vibrations produced by the curtains of a mechanical shutter. As said, fast exposures are possible, but there are downsides as well. The rolling shutter effect is one of those, and flash synchronization times are less fast due to the readout limitation.

Electronic First Curtain Shutter

There is a combination of a mechanical and electronic shutter possible. This is called an electronic first curtain shutter. As the name suggests, the exposure starts electronically and ends with the mechanical second curtain.

In a way, it’s a mechanical shutter with the benefits of an electronic shutter. There is no need to close the first curtain prior to the exposure, and thus no vibration due to the movement of the first curtain.

There is also less noise compared to a complete mechanical shutter, and faster flash synchronization times are possible. However, it is prone to image deformation, and banding can occur. It also has an effect on the bokeh, which gets deformed and becomes less attractive.

Some cameras don’t have a complete mechanical shutter anymore. They use the electronic first curtain instead of a true mechanical shutter.

Global Shutter

The downsides of the electronic shutter can be eliminated by recording the complete sensor in one single moment instead of line by line. This is called the global shutter.

For this, an extremely large bandwidth is necessary to accommodate all the digital information that is recorded. There is also a fast image processor necessary.

The benefit of a global shutter is the complete lack of a rolling shutter. Also, flash photography can be done with nearly every exposure time, provided that the flash duration is short enough.

There are also downsides. It requires a lot of power, which results in more heat production. There is also a lot of signal loss. Therefore, the dynamic range and ISO performance fall short compared to other modern sensors.

As of now, the Sony a9 Mark III is the only full frame consumer camera that has a global shutter. More will follow in the years to come. Also, the downsides will be addressed eventually.

Rolling Shutter Effect

Almost all types of camera shutters suffer from the rolling shutter effect to some degree, except the global shutter, of course. Due to the line-by-line readout by the electronic shutter, this system suffers the most from this effect.

The effect occurs when there is fast horizontal movement, either by the camera or the subject. When the sensor is scanned line by line, the movement of the camera or subject progresses during the scanning of the sensor. This results in deformation of the subject or any vertical lines in the background.

The rolling shutter effect is not influenced by the exposure time. It doesn’t matter if 1/500 second is used or 1/32,000 seconds. It’s only affected by the readout speed of the sensor. If a sensor readout is 65 milliseconds, which is 1/15 second, the rolling shutter effect will occur much faster compared to a sensor readout of 10 milliseconds (1/100 second).

The rolling shutter effect also occurs with older types of mechanical shutters that are made out of fabric. These focal plane shutters are much slower compared to ones that are made from metal.

The Type of Camera Shutter Doesn’t Matter

For most types of photography, it doesn’t matter which type of camera shutter is used. They all accomplish the task they're designed for: acquiring the exposure in the time that is necessary.

However, when more specialized photography is performed, the benefits and downsides become important. In those situations, it’s necessary to look at the camera shutter that best suits your needs.