Photography Tip—Controlling Background Exposure with Shutter Speed
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The distance between the flash and background must be enough, so the light does not illuminate the background. It must be beyond the range of the flash.
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The subject must receive most of its illumination from the flash.
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The flash exposes the subject while the level of ambient light exposes the background.
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Changing the shutter speed (remaining within flash synch speeds) will change the exposure of the background.
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Changing the shutter speed will not change the exposure of the subject since the slower shutter speed (1/250 second or slower) will always allow the entire duration of the flash (1/1,000 to 1/4,000 second) through the shutter.
As a digital photographer myself and having spent many years developing Graslon’s flash diffusers, I know that many of you are often confused about how to achieve balanced lighting on your subject and the background, simultaneously. The following concepts and techniques should help you to improve this balance, and take better photos.
In the following flash photo examples, notice the difference in the exposures of the background. The slower the shutter speed, the more illuminated the background. The exposure on the subject remains constant. How is this possible?
Try these techniques to duplicate these examples:
Under these conditions, the following effects occur:
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Remember the five components of exposure for flash photography: ISO, aperture, shutter speed, flash power and flash distance to subject. The shutter speed only affects the parts of the scene that are beyond the range of the flash. The flash power and distance only affect the elements within the flash range. You can use these characteristics to control exposure in different parts of your scene.
In the following photos, aperture, ISO and flash power were all the same. The photo with the darkest background was taken at 1/250 shutter speed. The photo with the brightest background was taken at 1/30 shutter speed.
Hint: Many times it is acceptable, even desirable, for the background to be blurry, so you may want to use very slow shutter speeds to brighten the background.
Hint: If your background is just too bright, then use a neutral density filter to darken the entire composition, and increase flash power.
About Graslon, Inc.
Much like the early pioneers of photography, Dan Naramor worked many months during the evenings and weekends looking for a way to make a flash diffuser that did a much better job of diffusing light.
All of his experimentation and effort led to discovering that all current flash diffusers in the marketplace don’t actually have much effect on the light from a flash. Most of the light rays travel as straight lines through the diffusion material. With this insight, Dan was able to develop a series of patent-pending, shiny surface mirrors that actually bend the light rays through his Graslon Flash Diffuser. The result is a larger light field because these mirrors spread the light across the entire area behind the diffuser material. Dan also created a convex diffuser material with 701 mini-lenses to ensure that the light is emitted from as much of the total surface as possible.
This breakthrough in flash diffusion technology has given digital photographers a tool that illuminates a scene or subject much more evenly. The Graslon Flash Diffuser simply does a better job of what a diffuser is supposed to do—diffuse the light.
Graslon Flash Diffusers come in three primary models: the Graslon Prodigy 4100D (Dome) and the 4100F (Flat) have a large diffuser, 8” x 5” x 3.” The Graslon Insight 4300D and 4300F are smaller versions with a diffuser that is 6” x 4” x 3.” The Graslon Spark Pop-up Flash Diffuser is made for DSLR cameras with pop-up flash units. Graslon also offers a series of amber dome and flat lenses and various other accessories.
Graslon Flash Diffusers are available from a number of photography retailers in many US states or can be ordered directly from Graslon on its Web site, www.graslon.com.
All photos copyright by Dan Naramor
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