Flash duration. Sounds a simple enough concept – but is it? Yes…and no. When I decided to write about this subject, I wrestled with how to explain the practice and principles of flash duration in a few words and (of course) pictures. Hope I’ve done a reasonable job because the better our understanding of the principles, the more control we have and the more creative we can be with our photography.
By now you already know that Flashes don’t just pop for a fraction of a second. This fraction has a value and its value determines how well it will stop motion (say a splash of liquid). This time is called T.5 (and T.1) and they are explained here.
So every flash manufacturer shares their T.5, and as with many devices there is some variance. Matt Kane of vela.io recently built a device for testing the actual flash duration using an Arduino board and a cheapo diode. The reason for this was to test how the output from strobes (and the vela LED airgap) behave.
Interestingly LED strobes behave differently than Xenon strobes and their fall off patterns is different. They are also much faster (see title image).
If you are planning on shooting water splashes* one of your primary concerns is flash duration. Usually when shooting high speed, you set your camera to bulb and shoot in complete darkness. When you want to take the photo, you pop the strobe. This makes the flash duration (actual time the flash emits light) act similarly to shutter speed – the longer the flash duration is, the more motion blur you’d get**.
Alex over at Photigy took four strobes to the test, ranging in price and specs to see how they stand up to freezing a water splash. A low res crop of the splash is posted right under the jump with our the name of the strobe which made it. See if you can match the photo to the strobe before watching the film or reading the full post over at Photigy.