The Biggest Problem With Global Shutter

No camera is perfect, but for me, the Sony a9 III is pretty close. Unfortunately, there is one problem that's holding this camera back.

It’s been over a year since the Sony a9 III made its groundbreaking debut as the first full frame global shutter camera. This innovative technology created waves in the photography world, offering capabilities that many professionals had only dreamed of. I’ve been using the a9 III since the day it was announced, and it has certainly lived up to the hype. In fact, I think this camera will be a definitive marker in camera technology history. However, after extensive use, there is one problem that not a lot of people are talking about—more specifically, the need for an adjustable flash timing and the effect that adjustment has in real-world flash use.

What Is a Global Shutter and Why Does It Matter?

Before we get to the issue at hand, let’s establish what makes the global shutter in the Sony a9 III revolutionary. Unlike traditional rolling shutters that capture an image by scanning the sensor from top to bottom, a global shutter captures the entire frame at once. This eliminates issues like rolling shutter distortion in fast-moving scenes or when panning. It’s a game-changer for sports, action, and wedding photographers who require precision and speed.

The a9 III’s global shutter brings another major advantage: the ability to sync flash at incredibly high shutter speeds, theoretically unlocking new creative potential. However, the technology isn’t without its hurdles, especially when working with flash.

Flash Timing: The Achilles' Heel of the Global Shutter

One of the most significant challenges I’ve encountered with the global shutter is flash timing. This issue arises when trying to synchronize flash output with the camera’s high shutter speeds—speeds far beyond traditional sync limits like 1/250 of a second.

Here’s where things get complicated: the process of finding the correct flash timing for a specific shutter speed and flash power setting is neither intuitive nor consistent. Adjusting the flash timing requires a meticulous process of trial and error, which can be tedious, especially under the time constraints of a professional shoot.

Comparing Traditional Sync With Global Shutter Sync

With traditional flash sync speeds, the workflow is straightforward. I set my camera settings—ISO, shutter speed, and aperture—for the ambient light. Then, I turn on the flash, set a general power level, and take a test shot. If the flash is too bright, I turn the power down; if it’s too dim, I turn it up. Simple and efficient.

With the global shutter, things remain just as simple as when working with traditional sync so long as you are at a 1/500 shutter speed or slower. But once you get to faster shutter speeds, things get a bit more complicated. You still do the same starting steps of getting your ambient exposure set, then getting your flash turned on to a starting power, and taking a test image. But before you can decide if the flash power is what you want, you first have to find the correct flash timing.

The way this works is you take a test image, then adjust the flash timing and take another test image. You then have to manually compare the two test images to see if the brightness of the flash has gone up or down. If the flash brightness has gone up, you adjust the flash timing, take another test image, and compare. You continue this process until you notice the flash power go down in brightness. At this point, you know that one adjustment back on the flash timing is the correct setting. Only then can you decide if the flash is too bright or not bright enough. If you need to make an adjustment, then you have to restart the entire timing adjustment, test image, and comparison process.

If at this point you are wondering if global shutter sync is more efficient than traditional sync and high-speed sync, you can see a comparison in the video below.

The Role of the Flash Curve

To understand the challenge fully, it’s essential to grasp the concept of a flash curve. When a flash fires, it doesn’t instantly reach peak brightness and then turn off; instead, its light output follows a curve. The duration and shape of this curve vary based on the flash’s power setting. Traditional flash systems are optimized for sync speeds like 1/250 of a second, where the entire flash curve fits comfortably within the exposure.

With the global shutter’s ability to sync at ultra-high speeds—up to 1/80,000 of a second—the exposure only captures a tiny slice of the flash curve. This is why the flash timing must be adjusted so precisely; the goal is to align the shutter with the peak brightness of the flash curve.

The Flash Power Dilemma

Here’s where the problem becomes even more complex: when working with such brief slices of the flash curve, adjusting the flash power doesn’t always produce the expected results. At ultra-high shutter speeds, different power settings can yield nearly identical exposures because the captured slice contains the same peak brightness. This undermines one of the primary ways photographers traditionally control flash output.

As a result, I’ve had to rely on alternative methods to adjust light levels, such as changing the distance between the flash and the subject, using ND filters for the flash, or adjusting the camera’s aperture and ISO. These workarounds can be effective but add complexity to the shooting process.

The Challenges of Multi-Light Setups

The difficulties don’t end with single-flash setups. Multi-light configurations become significantly more challenging when using the global shutter at higher shutter speeds. For example, if you are at a shutter speed of 1/80,000 and have a full-power main light and a quarter-power rim light, the flash output could actually be the exact same. And we can see that in practice. The images below were taken at 1/80,000, ISO 250, and f/1.8. The only difference is that one was taken at full power and the other was taken at 1/16th power.

Even though there is a very drastic difference in the flash output, the amount of light captured by the extremely fast shutter speed still gathers about the same amount of light. To add more trouble to the issue, if you have multiple lights and simply drop the power of one light far enough to access a different flash curve, you will end up not being able to see any light from that flash at all. This is because you can only have the flash timing set to capture a single curve peak.

Seeking Solutions: Charts and Future Innovations

To streamline the process, I’ve created a reference chart for my Godox AD200 Pro II that outlines the correct flash timing settings for various combinations of shutter speed and power. While this has saved time in the field, it’s a temporary fix rather than a comprehensive solution. The underlying issue remains: current flashes aren’t optimized for the demands of global shutter technology when you start to venture into higher shutter speeds.

Some flashes, like those from Sony and the newly announced Godox V100 Pro, already feature automatic flash timing adjustments. However, these advancements only address part of the problem. Ideally, we need a flash that has consistent flash timing for all power levels, as well as flash power controlled by peak power rather than peak power in combination with flash duration.

Conclusion

The Sony a9 III’s global shutter represents a monumental leap forward in camera technology, opening doors to creative possibilities previously unattainable. In all honesty, the issues at hand are not the fault of the camera itself but simply a consequence of this new technology pushing past the boundaries of what has ever been possible. We simply need flash manufacturers to catch up with this leap forward in innovation. So don’t get things confused and think that this tech is not worth the hassle. The camera works like any other camera when using shutter speeds of 1/500 or slower, which is already faster than any other mirrorless camera (aside from cameras using a leaf shutter). Also, some of these issues are not as drastic when shooting at higher shutter speeds just outside the 1/500 shutter speed. They just become more and more apparent as the shutter speed goes higher, being most noticeable at the max shutter speed of 1/80,000. But even with these pain points, the Sony a9 III is still hands down the best camera I have ever used for off-camera flash work. We just need the rest of the industry to catch up.