Flash Duration

Back when I taught college photography classes, I would force my students to do some practical flash duration comparisons. Why? Because flash duration is a very important thing to consider when choosing the right lights to make images. If the assignment requires moving fashion models, jumping athletes, or any other action, then the best choice for capturing sharp images are units that have short flash duration. Simply put, flash duration is the amount of time that the flash is on, typically between 1/200th and 1/3,000th of a second, but these vary widely with the amount of power output and type of flash unit. So please compare the flash durations at full power when shopping for or renting strobes. Shorter flash duration is the best choice for freezing motion.

The image above was lit with some old Elinchroms, one 250R (flash duration at 250 watt seconds = 1/6200th) and one 500r (flash duration at 500 ws = 1/4000th). Its nice and sharp!

And another of a pizza guy throwing that dough!

4 Comments

keano
April 8, 2015 3:49 am

I’m confused with a strobe with a short flash duration I can shoot within my camera sync range? I don’t need to go to 1/2000 to freeze motion?

Bruce
December 10, 2015 7:25 pm

Yes you use the flash sync speed which is actually 1/250 or 1/200th of a second and use the flash duration rather than the sync speed to stop motion. The paul c buff einstein is popular for this because its digital

James Godman
June 12, 2018 9:29 pm

Yes Bruce those Paul C. Buff units are great. Thanks for your reply.

James Godman
June 12, 2018 9:32 pm

Hello Keano – Sorry for the very late reply! You still need to shoot at your camera’s fastest synch speed (or slower). In a controlled environment that is lit by electronic flash, you would not use 1/2000 as a camera shutter speed to freeze motion. You do it by using strobes with a short flash duration (the actual time the flash stays lit). Imagine you are shooting in a black room with no light whatsoever. What difference would the shutter speed make? None. You could set the camera on bulb or the highest sync speed and get the same results with electronic flash. Hope that helps.

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