In all honestly, I think it’s magic.
What is Flash Duration?
First off, flash duration is different from high speed sync and to recognize that, you should check this out.
The flash duration, in very layman’s terms, essentially takes over for the effects of shutter speed in an image to a point. They are measured in fractions of a second the same way a shutter speed is. On that train of thought, if you have a faster shutter speed, then you can stop faster moving motion in camera. Likewise, if you have a faster flash duration, you can stop faster moving motion in camera.
To recap when it comes to exposures with flashes/monolights:
- Shutter speeds control the amount of ambient light in the scene
- Aperture controls how much of the flash actually effects the scene when set to manual mode (changes in TTL)
- ISO controls the overall sensitivity
- Flash output is flash output
Flash Duration in Action
See that image above? It stopped a very fast motion movement yet the shutter speed was very slow. Don’t believe me? Download the file. Do it!
At a 3 second shutter speed I was able to stop such fast moving motion. How? I was using the Einstein E640 monolight that has a very fast flash duration. The effects of the light going off made it able to stop the fast moving motion.
So Why is This Important?
Fast flash durations can help you stop very fast moving moments, get sharper images (with its stopping power combined with specular highlights) and yield you more creative freedom with when you can shoot. Afraid of using a flash outside during the day? Go into the shadows and give it a shot.