Here is a simple technique that, with practice, can give you greater flexibility in your pictures.
In the following photos, notice the difference in the exposure of the background. The slower the shutter speed, the lighter the background; however the exposure on the subject remains constant. How is this possible?
In order to achieve these results, the following conditions must be met:
- The background must be far enough away so as to not be affected by the flash. In other
words, the background must be “out of range” of the flash.
- The subject must receive most of its illumination from the flash.
If these two conditions are met, here is what you can achieve by simply changing your shutter speed and exposure:
The subject is exposed from the flash, while the background is exposed from ambient light. By changing the shutter speed (keeping within flash synch speeds) the exposure on the background will change. However, changing the shutter speed will not change the exposure on the subject, since the slower shutter speed (1/250 second or slower) will always let the entire duration of the flash (1/1000 to 1/4000 second) through the shutter.
Remember the five components of exposure for flash photography: ISO, aperture, shutter speed, flash power, and flash distance to subject. You can use these characteristics to control exposure in different parts of your scene. The shutter speed only affects the parts of the picture that are out of flash range. The flash power and distance only affect the components that are within the flash range.
In these photos, aperture, ISO, and flash power were kept constant. 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. Give this a try on your own; it’s a lot of fun to play with.
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 too bright, use a neutral density filter to darken everything and increase flash power.