1. What often distinguishes the beginning amateur from the advanced amateur and pro is a greater understanding of how to be creative with a flash and the available ambient light outdoors.
2. The advanced photographers knows, when he or she is taking a picture of a subject (person) outdoors, that the background and subject are lit by two different kinds of light (ambient and flash, respectively) and that each requires separate methods to expose them correctly.
The aperture and shutter speed settings on the camera determine the exposure of the ambient light in the background of the scene. The subject is lit by the flash, which must illuminate the subject accurately for the correct exposure of him or her.
3. Photographers, who understand this concept, use it first to make sure the subject is always exposed correctly with the flash, and second to then manipulate the exposure of the ambient light to photograph the exact same subject/scene, but with different moods or feelings.
Essentially, there is no longer a “correct” exposure for the scene. As the light from the flash continues to expose the subject correctly, then different apertures and shutter speeds can be selected to change the tonal quality of the background ambient light, and, therefore, the mood of the image.
4. For example, you’re shooting a subject outdoors without a flash. If you select the correct exposure for the subject, then you would be capturing too much ambient light, leaving the background too bright and blooming. Conversely, if you select an exposure based on the ambient light, then there wouldn’t be enough light reflected from the subject, making him or her too dark, with a loss of details. Add a flash to the equation and now you can select an accurate exposure level for the background and subject.
5. Try this experiment. A subject is framed against a western sky during dusk and twilight. You want to start this experiment when the meter reading of the sky matches your sync speed, which will probably be in the range of 1/250th, f/5.6 and ISO 200 to 400.
6. Before using your flash, however, shoot a few frames, exposing for the ambient light. As mentioned above, there won’t be enough light on the subject to expose him or her correctly, so they will appear dark in your test images.
7. The next step of your experiment is to use your flash, so you can put enough light on the subject for an exposure at f/5.6. Of course, the ambient light will begin to dim rather quickly. Soon you’ll have to change the shutter speed setting for the background to 1/125th and then 1/60th. Shoot a few test images at all these shutter speeds (with the flash) to improve your understanding of balancing the flash with the ambient light.
8. Your next learning experience is to underexpose and overexpose your scene deliberately. When the “correct” shutter speed for the ambient light is 1/60th, shoot a few images at 1/125th (background underexposed by one stop) and 1/250th (background underexposed by two stops). The subject is still accurately lit and exposed, but you’ve manipulated the exposure of the ambient light to create images with different moods: high contrast, dramatic, magical, etc.
9. As the background ambient light continues to diminish, requiring a 1/30th shutter speed, don’t manipulate the exposure with the shutter speed; use your flash instead. Decrease the power on your flash by one stop. This allows you to shoot at a faster shutter speed, although the ambient light is dimmer. You won’t have to switch from 1/60th at f/5.6 to 1/30 at f/5.6, but keep the shutter at 1/60th and switch to f/4. You achieve the same balance because your flash has been added to the formula as an additional exposure tool. You can easily duplicate this concept, as the ambient light continues to decrease. The “correct” shutter speed becomes 1/15th, but you still use 1/60th, but at f/2.8 and another stop of less power on your flash.
10. Now, you have a wide range of exposure settings you can use during dusk/twilight that will always expose your subject correctly, but allow you to be artistic with the ambient light.
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Photo by PhotographyTalk Member John Landolfi