Sony a9III Global Shutter Flash Timing

Key Concepts:

• Global Shutter: A camera sensor technology that exposes the entire image sensor simultaneously, unlike rolling shutters.
• Flash Timing: The adjustment needed to synchronize a flash with the global shutter at high shutter speeds.
• Flash Sync Speed: The fastest shutter speed at which a camera can properly expose an image with a flash.
• Flash Curve: The graphical representation of a flash's light output over time, showing how the light intensity rises and falls.
• Peak Power: The maximum intensity of light emitted by a flash during its flash curve.
• ND Filters: Neutral Density filters that reduce the amount of light entering the camera or emitted by the flash.

Main Topic: The Biggest Problem with Global Shutters - Flash Timing

Jason Vincent discusses the primary challenge he faces with the Sony a9 III's global shutter: flash timing at high shutter speeds. While the a9 III has lived up to the hype, the intricacies of flash synchronization beyond traditional sync speeds present a significant hurdle.

Traditional Flash Sync vs. Global Shutter Flash Sync

• Traditional Sync (up to 1/500th sec):
  1. Set ambient light (ISO, shutter speed, aperture).
  2. Set flash to a general power.
  3. Take a test image and adjust flash power as needed.
• Global Shutter Sync (above 1/500th sec):
  1. Set ambient light.
  2. Set flash to a general power.
  3. Take a test image.
  4. Adjust flash timing, take another test image, and compare until the brightest light is achieved.
  5. Adjust flash power if needed, then repeat the flash timing process.

The Problem: Tedious and Unpredictable Flash Timing

• There's no formula for flash timing adjustment.
• Changing flash power or shutter speed requires re-adjusting flash timing.
• Different flash brands or power levels necessitate unique flash timing settings.
• Example: If a flash timing setting of 700 works at full power and 1/80,000 sec, changing the flash or its power will require a new setting.

Solution: Creating a Flash Timing Chart

To streamline the process, Jason created a chart mapping flash timing settings for various combinations of shutter speed and flash power (in full stops). This allows him to:

1. Set camera settings.
2. Set flash to a starting power.
3. Consult the chart for the appropriate flash timing.
4. Take a test image and adjust flash power, referencing the chart again for the new flash timing.

The Flash Curve Complication

Flashes have a flash curve, where light intensity rises to a peak and then falls. Traditional sync speeds (e.g., 1/250th sec) capture the entire curve. However, at high shutter speeds (e.g., 1/80,000th sec), only a small slice of the curve is captured.

• Adjusting flash power primarily changes the duration of the flash, not necessarily the peak power.
• Multiple flash power settings can yield the same peak power.
• Example: Images taken at different power levels (full, 1/2, 1/4, 1/8) at 1/80,000 sec can have similar exposures.

Implications of the Flash Curve Problem

• Loss of Power Control: Adjusting flash power becomes ineffective at high shutter speeds.
• Alternative Methods: Adjusting light levels requires changing the distance to the subject, using ND filters on the flash, or adjusting aperture and ISO.
• Multiple Light Setups: Difficult to balance lights with different power levels (e.g., full power main light and quarter power rim light) because they can produce the same output at high shutter speeds.
• Incompatible Lights: Combining different lights is problematic because their flash timing settings likely won't match.

The Future of Flash Technology

• The global shutter technology pushes flash designs beyond their intended limits.
• Flash companies need to evolve their designs to match the new sync speeds.
• Flashes like Sony's and the Godox V100 Pro automatically adjust flash timing.
• Ideally, flash power should be controlled by the peak power, not the duration of the flash.
• "What we need is for every flash power to have its peak power at the same timing, and we need the power of the flash to be controlled by the peak of the power instead of being controlled by the peak of the power in combination with how long the flash is on."

Comparison to Traditional Sync and High-Speed Sync

Jason has a separate video comparing global shutter sync to traditional sync and high-speed sync.

Specific Equipment and Future Plans

• The current chart is for the Godox AD200 Pro Mark I (and seems to work for any AD200 and Flashpoint variants).
• Jason plans to create more charts for other lights in the future.

Conclusion

While the global shutter on the Sony a9 III unlocks creative possibilities, it introduces challenges with flash timing at high shutter speeds. The primary issue is that adjusting flash power becomes ineffective, requiring alternative methods for controlling light levels. Flash companies need to innovate to address these challenges and optimize flash designs for global shutter technology. Despite these challenges, the technology is still worth it, especially when using lower shutter speeds like 1/500th of a second.