Sony produced what can be described as a camera game-changer with its current flagship, the Sony a1. Although this camera offers a plethora of new features that most reviews are raving about. One of its most notable features has remained a bit under the radar. This function is to increase the flash sync speed to 1/400th of a second shutter speed.
The Sony a1 is one of the best full-frame mirrorless cameras on the market. Not only can it record high-resolution 50 megapixel files, but it can also capture that much resolution at 30 frames per second. It was only until recently that we thought that speed and high resolution were an impossible combination, based on current technology. You could have a high-resolution camera that captures a lot of detail, or you could have a low-resolution camera that shoots extremely fast for high-speed situations. Sony has managed to do both in one camera.
In addition, Sony also managed to cram 8K 30p and 4K 120p into 4:2:2, 10-bit recording. Essentially, the Sony a1 is an incredible camera system. However, these features are obvious upgrades and inevitable in the grand scheme of things. Most everyone expected Sony to produce an 8K-compatible camera system, but I doubt anyone thought Sony would improve the shutter mechanism and sync speed in the Sony a1.
What is a focal plane shutter?
A focal plane shutter is essentially the shutter mechanism found in almost all DSLR and mirrorless cameras. A focal-plane shutter exists in the camera and sits in front of the camera sensor. There are two sections for a focal plane shutter and they are called the first curtain and the second curtain.
The first curtain falls open to reveal the full sensor, after which the second curtain falls to close the shutters again. The time it takes to open and close the shutter depends on your shutter speed.
The main advantage of slit shutters is that they can handle faster shutter speeds than leaf shutter mechanisms (discussed below). Most high-end DSLR and mirrorless cameras can handle shutter speeds up to 1/8000s, which is significantly faster than leaf shutter cameras.
The other advantage of slit shutters is that they work in-camera. This means that almost any type of lens can be attached and the shutter mechanism can still fire. You can even use pinhole body caps on the camera and the shutter will still fire so you can expose an image.
The disadvantage is that a focal-plane shutter can only remain fully open up to a certain speed. For most cameras, this shutter speed is 1/200s. Above this speed, the shutter blades will no longer open fully as it moves down the sensor to expose the image. The aperture in the shutter gets smaller as you increase the shutter speed. This isn’t a big deal unless you’re shooting with flash. If the aperture in the shutter blades is smaller than the sensor, the entire sensor will not be exposed when the flash is fired.
As you can see in the equation above, a lot of the flash hits the shutter blades rather than the sensor when you’re shooting faster than the sync speed. To solve this, you can use a function called high-speed-sync. In this mode, the flash fires multiple times quickly to track the shutter blades as they move past the sensor. Unfortunately, this feature significantly reduces flash power, making it less than ideal in many situations.
What is a leaf shutter?
A leaf shutter is relatively rare when it comes to camera systems. The biggest and most obvious difference between a leaf shutter and a focal-plane shutter is that the leaf shutter works in the lens rather than in the camera. This severely limits compatibility with third parties. Another obvious difference is the structure of the leaf hatch.
Focal plane shutters move over the sensor in one direction, usually from top to bottom. Leaf shutters open and close in a circular motion somewhat similar to how diaphragm blades open and close. It is this design difference that makes the biggest difference. Unlike slit shutters, leaf shutter mechanisms have no flash sync speed limit. Leaf shutter lenses can sync with the flash at any shutter speed it can manage.
For example, current Hasselblad lenses can synchronize the flash even at a shutter speed of 1/2000 sec. without the need for a high-speed sync mode. The downside to leaf shutters is that the highest speed currently available is 1/2000s, and this is significantly lower than what slit shutters can achieve, which is 1/8000s.
How did Sony manage this?
A camera shutter mechanism generally works with a spring-loaded system. In a focal-plane shutter camera, the two curtains load and flash when you press the shutter button. The spring-loaded system has worked extremely well in cameras for decades. However, this system has not been updated for a long time.
Inside comes the Sony a1 with its dual-driven focal-plane shutter. The shutter mechanism in this camera works with a spring-loaded system and also with a magnetic system. The spring-loaded system is active for most shutter speeds, both fast and slow. The magnetic system is only active between shutter speeds of 1/320s and 1/400s.
These are the two fastest points with which the Sony a1 flash can synchronize in full frame mode. The magnetic system allows the shutter curtains to move faster across the frame. The first curtain can open quickly enough that by the time the second curtain is ready to close, the entire sensor is open for exposure.
This is the main difference. The magnetic system can move the roller shutter curtains faster than the standard mechanism. That extra speed ensures that the entire sensor is open for exposure, as opposed to parts that are blocked by the shutter blades.
Why this is a big update?
The Sony a1 is currently the only full-frame camera on the market that can sync with flash at 1/400th of a second shutter speed. This is double the speed of most full-frame cameras, including Canon and Nikon flagship systems. This sync speed can further increase to 1/500s shutter speed when shooting in APS-C mode. This kind of speed is on par with some leaf shutter lenses.
Interestingly, even with this higher sync speed in the Sony a1, the camera shutter is durable enough to manage over 500,000 cycles. Although it’s important to mention that Sony has not disclosed the durability ratings for the shutter mechanism when flash sync priority is enabled.
Nevertheless, for many working photographers, this increase in sync speed offers more of a real benefit than dynamic range improvements or an increase in resolution.
Having a lot of resolution can be great, but after a certain point a few more pixels make little difference to how you shoot and the results you produce. Even with dynamic range, most cameras now offer enough flexibility that an extra half-stop won’t make much or no difference to the workflow. Features like megapixels and dynamic range can make for great headlines, but in the grand scheme of things, it’s just marketing. Even smartphones can now shoot up to 100 megapixels and above.
The increase in synchronization speed brings a real change in the workflow. You can shoot with a higher shutter speed regardless of the type of flash you use. You can also postpone the need to shoot with high-speed sync by a full stop. This is especially useful when shooting in a controlled or studio-based environment.
If you were shooting in a studio for a long time, the maximum shutter speed you could probably choose was 1/200s. Being able to shoot with a faster shutter speed in a controlled environment will most likely reduce potential problems. For example, if you’re shooting people, introducing motion into the shots is less likely to cause motion blur.
This is without a doubt one of the best and hardest technological leaps we’ve seen in a long time, and Sony should be credited for it.
This is a huge leap for working professionals and the best part is that it won’t be long before this feature appears in cheaper cameras. As the cost of features becomes less expensive, we can begin to see this becoming the default sync speed for flash.
What isn’t clear at this point is whether Sony can take this dual-driven mechanism further. It’s arguably reasonable to assume that the magnetic system can probably handle even faster shutter speeds. However, it was probably durability issues that limited the sync speed to 1/400s.
Hopefully, we’re just at the beginning of what’s possible with magnetic shutter drives. Who knows, Sony’s next flagship camera might even sync the flash at 1/1000s.