Flash is a very powerful tool for outdoor photographers. While ‘sweet light’ is often available naturally, the midday sun or less than flattering outdoor light may be all that is available and this often presents the need for additional light sources.
Reflectors are great as a tool to bounce light into shadow areas and lessen contrast from the natural light, but reflectors are not always the best tools. Most of them have a limit on reflectance ability or rather the measurement of how much light bounces off in comparison to the amount of light that hits the reflectors varies.
Silver and gold will bounce back more light that white, but they produce much contrastier light than soft light from a white reflector. In addition, reflectors can create their own highlights and resulting shadows depending on their bounce ability or reflectance value and position.Often when shooting outdoors and using the outdoor light as your main or key light, you really only want to supplement the natural light by filling in shadows and lightening them rather than creating new highlights and shadows.
This makes on-camera flash a great option in this scenario. It can be used in a manner where it does not create its own shadows and highlights and instead just supplements the existing light by lightening shadows.
Today’s state-of-the-art flash units are very sophisticated electronic devices but are really fairly easy to use if you understand the basics of flash. Flash and ambient light are two separate light sources with each controlled for the most part, individually by settings both on-camera and on the flash.
When using your camera to take a photograph you can use your aperture or shutter speed to adjust exposure to brighten or darken the picture. With flash, it is common to separate those tools when controlling either the flash or ambient exposure.
Shutter speed has no control over flash exposure. When the shutter opens and begins exposing the flash fires quickly and the shutter remains open until it has completed the ambient exposure. It makes no difference whether the shutter is open for 1/100th of a second or 10 seconds, the flash fires when the shutter opens and has completed its light burst before the shutter closes. This confirms that shutter speed has no control over flash exposure.
The aperture on the other hand, does control flash exposure. If you are using your flash in manual flash mode for consistent output, then increasing your aperture or decreasing your aperture does control flash exposure because it either allows more light through the lens or less light when shutter speed remains constant.
Just keep in mind that if you use your aperture to lighten or darken your flash exposure that you need to make an equal adjustment on your shutter speed to maintain the same ambient light exposure. That means if you metered your scene and came up with f/11 @ 1/125 and you want to brighten your flash exposure while using manual flash by changing it to f/8, you now need to adjust your shutter speed to 1/250 to keep the same ambient exposure.
Stay tuned for a series on various ways to use your flash outdoors. And if you have any flash tutorials you would like to share, please let us know.
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