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Bright sunlight, used as the only means of illumination for an exposure, can produce deep objectional shadows on a subject. When a flash unit is used as a fill-in source of illumination, it reduces these shadows and is known as synchro-sunlight photography.

Improperly handled, the synchro-sunlight technique can produce an effect that makes the photograph appear as if taken at night with a single flash. This effect occurs when the flash illumination is more intense than the sunlight.

The first step for proper exposure with synchrosunlight is to calculate the correct exposure for daylight, and set the shutter speed and f/stop as though a flash is not being used; however, keep in mind when using a focal-plane shutter, the shutter speed must be synchronized with the electronic flash unit. Avoid using a fast film in bright sunlight when using a camera equipped with a focal-plane shutter. In this case, you are limited only to your aperture to control the exposure of the film, because your shutter speed is nonadjustable. A leaf shutter has an advantage over a focal-plane shutter. When a leaf shutter is used, it provides more control over depth of field since the shutter synchronizes at all shutter speeds.

When you are using an automatic flash, the same principles apply for synchro-sun that were explained in the section for lighting ratio. The sun is used as the main light, and your camera settings are determined directly from your light meter. The easiest method is to set the film speed (ISO) on your flash unit to twice the film speed being used for a 3:1 lighting ratio and four times the film speed being used for a 5:1 ratio. A fraction of the manual power output can also be used to achieve the desired lighting ratio.

Remember to compensate your exposure by opening up two f/stops for a backlit subject and one f/stop for a subject that is sidelighted when taking your light meter reading from a distance. For color photography, you should normally use a 2:1 or 3:1 lighting ratio. For black-and-white photography, a ratio of 3:1 to 5:1 is acceptable.

MULTIPLE-FLASH UNITS

Multiple flash is the use of two or more flash units fired in synchronization with the camera shutter. The flash units can be auxiliary flash units, connected to the camera by extension cords, or they can be slave flash units. Slave units usually have self-contained power sources and are fired with a photoelectric cell when light from a master flash unit strikes the cell of the slave unit.

With multiple flash, exposure calculations are based on the distance between the subject and the flash unit that produces the most intense illumination to the subject; therefore, you can have numerous auxiliary flash units or slaves for a scene and only calculate your exposure from the mainlight source. All other flash units should be equidistant or at a greater distance from the subject as compared to the flash unit on which the exposure is based.

When two flash units of equal intensity and at equal distance from a subject illuminate the same area, the exposure for one unit should be determined and then the exposure should be halved because twice the intensity of light is reflected from the subject.

OPEN FLASH

Flash pictures can be made without the camera shutter and flash being synchronized, using a technique called open flash. In the open-flash method, the camera shutter is set at T or B, the shutter is opened, the flash unit fired, and the shutter closed. The open-flash technique is sometimes used when the level of light over a large scene is very low or at night. This method of flash photography allows the photographing of large scenes that ordinarily are quite difficult to illuminate with artificial light. The photographer can walk into a scene with the flash unit and illuminate sections of the scene or the entire scene. Any number of flashes can be used during the exposure while the shutter remains open. A silhouette of your body can be recorded if your body gets between the flash and the camera.

To arrive at the exposure for an open-flash picture using a manual flash, determine your flash-to-subject distance and f/stop. Keep the distance equal to the objects being illuminated when using manual flash; for example, when the f/stop for the scene is f/5.6 based on a flash-to-subject distance of 10-feet, every flash within the scene should be 10 feet from that section of the scene being illuminated, When an automatic flash is used, the flash automatically shuts off when the proper amount of light is reflected from the subject, providing the object is within its distance range. When you are using a manual flash, the exposure for open flash is determined as previously discussed. This is true unless two or more flash units with equal intensities are used at equal distances, or two or more flashes from the same unit at the same distance are used to illuminate the subject.







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