Digital Photo Academy

Learn How To Use Your Digital Camera

Stop Action Flash, Flash Duration and Trip Shutters

Digital Photo Academy and LivinginHD present a free monthly series of photography webinars on Your host, John Bentham answers many questions live during the webinars. Additional questions and answers are posted here on You can also view the archived webinars for reference.



Photograph by Josh Anon, DPA Instructor, San Francisco


Stop Action Flash, Flash Duration and Trip Shutters, Stop Action Photography, High Speed Photography

To stop action in a bright room, or when shooting outside in daylight you need a fast shutter speed, 1/1000 of a second or higher depending on the subject. But to stop action in High Speed photography you need a Fast Flash Duration. Shutter Speed is the actual speed, the duration of time the camera shutter is open letting light hit the sensor. Flash Duration is the actual duration of time that the flash is lit. These are two very different things. Camera shutter speeds can be as high as 1/4000, or 1/8000 of a second, but flash duration speeds can be much faster, upwards of 1/10,000 of a second. These very fast flash duration speeds are what photographers use to freeze water droplets, or freeze the wings of a Hummingbird in flight. There are a number of factors that determine flash duration. 1. The equipment produced by the manufacturer: There are a few units available specifically designed for fast action photography to achieve a short (fast) flash duration. 2. The lower the power output of the flash unit the faster the flash duration will be. Capacitors store the energy in the flash and release it when the flash is triggered. It takes a certain amount of time for the energy to release, thus less energy stored means less time to expend, resulting in a shorter flash duration. The shorter the flash duration means the more stopping power a flash will have. 3. When using on-camera dedicated Speedlights, which have flash sensors built into the unit, the flash duration is shorter the closer the subject (object being photographed) is to the camera. The Flash unit measures the light bouncing back off the subject and cuts off the flash output when it measures a correct exposure. Obviously a closer object requires less light that one further away, thus a closer object will result in a faster flash duration. To stop action you use the lowest power setting you can to still achieve a correct exposure. Very often these exposures are made in a blacked-out room to avoid any ambient light from influencing the exposure, also allowing for a slow shutter speed which means the camera shutter can remain open indefinitely without exposing the sensor until the flash fires.



Photograph by Allen Birnbach, Denver, DPA Instructor

Trip Shutters

When doing high speed photography very often the action you are trying to record happens faster than the human eye or your brain can see, or comprehend. Hence the need for an activated shutter, one that is triggered by an event rather than the human hand. Photographers utilize a number of different devices for this purpose, commonly sound, vibration, contact or beam interruption (motion) activated shutters. As each name suggests these devices are triggered by an action (eg: sound) causing a reaction (flash and camera operation) resulting in an exposure.



Photograph by Milton Heiberg, Orlando, DPA Instructor

Submitting your photographs for webinar consideration: Specifications and requirements.

Anyone can submit photographs for inclusion in the DPA, LiHD Webinar, Online Photo Class Series. If you would like to submit your photographs for an upcoming webinar, please read the following. Each webinar has a specific theme or topic. First go to, Tip of the Day, to determine the theme for the next webinar. Then review the submission requirements below and submit your photographs to Note that webinars are edited and formatted days in advance, thus please submit your photos at least a week in advance of the webinar, late submissions can not be added. Photographs are chosen, and edited, for their applicability to the webinar theme, artistic and technical merit, and content length. If your photograph is NOT chosen, it will be archived and may appear in a more appropriate future webinar.

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Please include your name and city in the image file name as below:

Please also include brief captions including subject, location and any pertinent tech info.
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