Lighting in Photography Part 10

Flash for the Main Light

When using flash as the main light and ambient light for the fill, it is important to remember that you are balancing two light sources in one scene. The ambient light exposure will control the exposure on both the background and the subjects. The flash exposure will affect only the subjects.

At Twilight. If the light is fading or the sky is brilliant and you want to shoot for optimal color saturation in the background, overpower the daylight with the flash. This is where the flash becomes the main light and the ambient light becomes the fill light. Returning to the situation above, where the daylight exposure was 1/30 second at f/8, you could adjust your flash output so your flashmeter reading was f/11, one stop more powerful than the daylight. Then, you would set your camera to 1/30 second at f/11. At these settings, the flash would provide the main light while the soft twilight provided the fill light. This technique works best when the flash is diffused and at an angle to the subjects so there is some discernable lighting pattern. (Note: The only problem with this technique is that you will get shadows from the flash. This can be acceptable, however, since there aren’t really any shadows coming from the twilight.)

On Overcast Days. When the flash exposure and the daylight exposure are identical, the effect is like creating your own sunlight. This technique works particularly well on overcast days when using barebulb flash. Position the flash to the right or left of the subject(s) and raise it up for better modeling. If you want to accentuate the lighting pattern and darken the background and shadows, increase the flash output to 1/2 to one stop greater than the daylight exposure and expose for the flash exposure. Do not underexpose your background by more than a stop, however, or you will produce an unnatural nighttime effect.

Many times this effect will allow you to shoot out in open shade without fear of creating eye sockets that are hollowed-out by shadow. The overhead nature of the diffused daylight will be overridden by the directional flash, which creates a distinct lighting pattern.