Slow-Sync Backgrounds

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Flash is a great tool to use to control backgrounds when working with macro subjects. Whether the flash is mounted on the hot-shoe of the camera, or on a specially manufactured bracket used for close-up photography, the distance from the subject to the flash is short. When working with small apertures that are necessary when doing macro work to attain adequate depth of field, the light from a flash falls off quickly. This results in backgrounds rendered in black. This can be quite dramatic if the subject is vividly colored, as it seems to “jump” off the page.

Problems begin to arise if the subject has many dark tones, especially if the dark tones make up its perimeter. The result is the subject merging with the background, making it hard to differentiate where the subject and background separate. One solution is to use another flash as a rim light aimed at the subject from behind. It creates a halo of light, making the subject’s outline more obvious. The problem is you need to carry another flash and you’d have to calculate flash distances to arrive at its proper exposure.

A much simpler solution is to adjust the camera’s shutter speed to allow more ambient light to reach the film. Just because the camera synchs at 1/250th doesn’t mean that all flash images must be shot at that speed. While it’s true you can’t exceed a camera’s flash sync speed unless you have high speed synch capability, you can use any shutter speed that’s slower. The exposure for the close up subject should be determined by the flash and aperture setting while the background can be lightened based on the shutter speed.

In the two images seen here, both were shot with flash. For the first, I used the camera’s recommended synch speed of 1/250th, which produced a black background. As a result, sections of the wings and most of the antennae merge in tone with the background. For the second shot, I spun my shutter speed to 1/30th, which allowed the available light inside the butterfly pavilion to be recorded. The next time you’re using flash, experiment with different shutter speeds to see how you can improve your images.


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