Using flash as fill in light

Flash may be used not only in conditions of dim ambient light, but also as supplementary light in the daytime. Many times we have the opportunity to take contre-jour pictures [against the light, the sunlight is behind the subject], and in most of the cases the subjects can be so dark in the picture that they show little or no detail. If the shadow covers a large part of the subject, the effect can be distracting and unattractive. In this mode the flash fires even when there is enough available light to take the picture.

Electronic flash improves the color balance of the image, improves color saturation and may help increase sharpness. Fill-In Flash is a setting on most digital cameras that will produce a short burst or bursts of light as you snap your photograph. This will provide lighting to avoid your objects in the foreground from being shadowed and the colors will appear brighter and more vibrant.

Many of the modern cameras and the advanced flashes can automatically calculate the fill in light given by the flash, but in order to fully control the final image, a combination of TTL flash and a measurement device for the indoors will provide the finest images.

There is one basic principle that should be understood, namely that flash exposure compensation actually represents a simultaneous double exposure. One exposure is suitable for the ambient light, a second exposure being given by the flash light. If the ambient exposure is given by the relationship between shutter speed and aperture, the flash exposure is controlled by the flash power, the light interval given by the flash, the manual or auto exposure, and finally by the distance to the subject, or the employed diaphragm aperture. Shutter speed has no influence on this illuminating mode as long as this is the one indicated for the flash synchronization.

You should pay more attention especially in the open air, because the flash power is much smaller than in a studio or in a closed space. Since there are no objects outside to reflect the flash light in the direction of the subject, the flash power should be negatively reconsidered. Given that there is no mathematical formula for it, any user should test his flash under these conditions.

Finally, this exposure technique gives you more details in the shadows than you may obtain using overexposure or other exposure automatisms. With a little experimenting, everyone can use it once they are familiar with the efficiency of their flash in the open air.

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