Off-camera flash

Locating flash away from the lens solves problems

Electronic flash units are most-commonly located in just about the worst-possible place for photography - near the camera’s lens. Many cameras have built-in and pop-up flash situated a mere two or three inches from the lens, while other accessory units mount on a hot shoe at a slightly-greater distance from the lens.

WHY IS LOCATING FLASH NEAR THE LENS BAD?

Poor location of the flash is probably the number-one cause of poor flash pictures, and it is harder to find a worse location than near the lens. Light reflecting directly off a subject can cause “hot spots” - flash glare from shiny or even-partially reflective surfaces, such as human skin. The problem of red-eye is a direct result of the flash’s proximity to the lens. The overall lighting of a subject is often featureless and flat, since such straight-on light tends to wash out texture. For extreme close-up photography, the flash cannot be properly aimed at a subject because of parallax - the lens is aimed at one thing and, because of its distance from the lens, the flash is aimed at another. Another related problem is that direct flash as the primary light source produces contrasty, harsh light, without the softening effect that is especially desired in people pictures.

WHAT CAN I DO ABOUT THE PROBLEM?

The solution is to move the flash head further away from the lens.

Unfortunately for many compact camera owners that have built in flash heads, the light cannot be aimed or directed anywhere other than straight ahead. There are fewer remedies to overcome the problems of direct flash with these cameras.

Many camera designs permit the photographer to fire the flash at a greater distance from the lens. One means of accomplishing this is through the use of a cord that plugs into the flash unit (called either a flash synch [sync] cord or a flash remote cord - shown above) and also connects to a "synch terminal" (flash synchronization terminal) located on the camera body. Remote cords are generally not provided with either the flash or the camera, and must be purchased separately. When the shutter is tripped, a signal races through the cord, triggering the flash. The flash unit can be hand-held at some distance from the lens, although this is cumbersome since you normally operate a camera using both hands, but it has the advantage that its light can be directed off-axis at the subject. A more-convenient and practical solution is to mount the flash unit on an accessory bracket especially made to locate it away from the lens.

Off-camera flash can also be used without a hard-wire connection to the camera, using an infra-red slave system. An infra-red transmitter is mounted to the camera’s hot shoe and its cable is connected to the synch terminal. When the shutter is tripped, an infra-red signal is transmitted to a receiver attached to the flash - which can be at considerable distance from the camera - and triggers the flash. The signal is similar to that issued by TV or VCR remote controllers.

Another method of off-camera flash involves two or more flash units, one of which (the “master flash”) is connected directly to the camera - either on-camera by hot shoe or off-camera by remote cord - and the other (known as the “slave”) is not. The flashes can be wire-connected in series using long triggering cords, or an optional accessory known as a wireless slave flash controller, which has a built-in light sensor, can be attached to the second flash. It senses the burst of light from the first flash, triggering the slave unit to fire in unison with the master flash for the same duration. The slave flash can be used to either provide additional subject illumination from another angle, or to light up another part of the scene, for instance a dark background or other persons at various distances from the master flash.

THE BENEFITS OF OFF-CAMERA FLASH

Operating the flash off-camera at a distance from the lens solves many of the problems of camera-mounted flash. Red-eye is eliminated. Since the flash reaches the subject at a different angle than the lens (more from the side rather than straight-on), features are “modeled” better, with the off-axis lighting enhancing details and texture, and giving a degree of shading to three-dimensional subjects. Hot spots are reduced or eliminated altogether. Off-camera flash can be extremely useful in situations requiring the use of fill flash.

Even with the flash positioned away from the lens, its lighting is still harsh since it is a direct, point source of light. Shadows will be hard-edged and dark. See our section entitled Softening the harsh light from a flash for solutions to this problem.