Slave flashes fire automatically when the main flash, which is the built-in flash on cameras that do not have detachable flashes, fires. Electronic sensors in the slave flash detect the firing of the main or triggering flash and then fire the external slave flash.
Limits Of Built-in Camera Flashes
Even the most powerful built-in flash usually cannot light an area more than about 30 feet away. In fact, many of the built-in flashes on ultra-compact cameras have a maximum flash range of no more than about 15 feet. Slave flashes are particularly helpful when shooting in large rooms or rooms where the ceilings are higher than about 10 feet. In these situations, the camera's built-in flash power is dramatically cut by having to cover large spaces.
The added flash power of a slave flash also allows photographers to bounce light off a white ceiling or a white 3x5 card attached to the flash head or a reflector in order to soften shadows and produce more appealing photos. And though bounce lighting is often desirable, employing it reduces flash power because the light has to go from the flash to the ceiling or reflector or card and then to the subject rather than traveling directly from the flash to the subject.
Let The Guide Number Be Your Guide
The higher the guide number the more powerful the flash. Most flash manufacturers state the guide number in the user's manual. Guide numbers are expressed in the number of feet or meters the flash can reach, typically, at ISO (film speed) 100. (To convert a guide number in feet to meters, multiply it by 0.328; one in meters to feet, multiply by 3.28).
The guide number is determined by multiplying the aperture by the distance. Therefore, if an aperture of f8 yields a properly exposed photo when the flash is 10 feet from the subject, then the guide number is 80 if the (zoom) lens is set at 35mm.
The distance is determined by dividing the guide number by the aperture. So, if the guide number is 80 and the aperture is set at f4, then the flash should be 20 feet away from the subject. The aperture is found by dividing the guide number by the distance. So if the slave flash is 15 feet from the subject, then use f5.6, which is as near to f5.3 as the photographer can get.
Photographers can increase the range of their flashes simply by increasing the ISO they use. So, using ISO 200 gives more exposure than ISO100 and using ISO 400 gives more exposure than ISO 200.
A Choice For Ultracompact Cameras
For owners of ultracompact cameras, the Metz Mecablitz 28 CS-2 is a possible choice. It has a guide number of 72 at ISO 100 when used with a lens that has a 35mm focal length and 92 feet with a lens that has a 85mm focal length. The 28 CS-2's smaller size is compatible with smaller digital cameras. Photographers should do comparison shopping online for a flash.. Prices vary widely depending on which online seller the buyer chooses.
Ways Of Attaching A Slave Flash
Even though this article centers on using slave flashes in combination with built-in flashes, they can be used with almost any digital or film camera. They mount most commonly by attaching to a permanent mount called a hot shoe. Not all cameras have a hot shoe and those with a built-in flash do not. A hot shoe allows communication with a camera so that when the flash is attached and the shutter button depressed, the flash fires. Less commonly they mount by a syn cord, one end of which attaches to the camera's pc (Prontor and Compur) socket (i f the camera has one) and the other end to the slave flash.
When the camera has a built-in flash, the photographer uses the bracket that comes with the slave flash and screws into the camera's tripod socket on the base of the camera. Then the photographer slides the slave flash into a slot on the bracket. Today's digital slaves designed to work with built-in flashes fire whenever the built-in flash goes off. Some older flashes require that the main flash face the slave flash for the slave flash to be triggered.
Slave flashes are not restricted to being mounted on cameras. They can also be placed on tripods or light stands. And multiple slave flashes can be used to create a photo.
Use Caution When Using Flashes Previously Used With Film Cameras
Though triggering devices can be purchased to make flashes that were used with film flashes slave flashes, caution must be used. The reason is that some flashes constructed to work with film cameras needed power of from 200 to 400 voltages to operate. But today's digital cameras need less than six volts to work. Therefore, using a high-voltage flash with a digital camera could destroy the digital camera's circuitry by overheating it.
Photographers who are unsure about the voltage of a flash that was previously used with a film camera should read the flash or camera owner's manual to determine the voltage. Or ask a reputable and knowledgeable photo dealer about the flash. If no answer comes from these sources, the Wein company sells the Safe Syn, a device that brings the voltage of an electronic flash from around 400 volts to fewer than six.
Or the photographer can simply buy a slave flash designed to work with the latest generation of digital cameras.
Many Flashes For Digital Cameras Fire Two Bursts
Another note about flashes for digital cameras. Most fire two bursts of light rather than just the one usually required for film cameras. The first firing called a pre-flash is meant to gather a variety of data such as the white balance or the flash-to-camera distance. The second flash burst is to actually to take the photo. It's helpful for photographers to know whether their digital cameras require one or two bursts before the photo is taken.
Finally, if a photographer has not bought a digital camera yet, consider buying one that has a hot shoe. Photographers can then buy the flash that suits their needs.
Linda N. Riggins - I have written freelance articles for Victorian Homes,Catholic Digest, the Old Farmer's Almanac, Fine Homebuilding, the Christian Science ...
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