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An electronic flash has a maximum distance that it is capable of illuminating. There's also usually a close point where it will start to become too bright and overexpose the subject. The distance from the closest to the furthest point that it can illuminate is the flash range. The range can be increased by using a faster film or more sensitive CCD, and reduced by diffusing the light source using ND filters or material. The range quoted is usually based on using ISO 100 film or a CCD with equivalent sensitivity. APS cameras are, for some reason, quoted using ISO 200 film.
The maximum shutter speed that can be set when using electronic flash. You can use shutter speeds below this setting but ones above will make some of the picture dark because the shutter would have partially closed before the flash had fired.
A socket on the camera used to plug-in an electronic flash gun cable so that the flash can be triggered at a distance from the camera.
Indicates the energy content of the storage capacitors in an electronic flash. One Joule is the light output given by one watt burning for a second. Therefore a flash unit with a storage capacity of 300 Joules can supply the power to light a 300W lamp for one second. It doesn't take into account any electrical loss between the flash capacitor or flash tube, or the efficiency of tube and reflector.
A light that is positioned close to an electronic flash so you can roughly preview the effect of the flash before taking a photo. Usually supplied with studio flash although a few on-camera guns have a strobe to assist.
Indicates the output, or power, of an electronic flash. You can use the guide number to work out the aperture or flash to subject distance by dividing either into the guide number.
A flash sync connection found on some older cameras that was used for bulbs, not electronic flash.
The time it takes for an electronic flash to fully recharge. Automatic thyristor flashguns have special circuits that store unused flash ready for the next shot so recycling speeds up. This is essential for fashion and sports photography, but less so for still life. The recycling time of more powerful or manual units is usually longer.
A meter used to measure the light that is emitted from an electronic flashgun. The meter suggests what aperture should be used to obtain a correct exposure. Some meters are purely for flash, others are multipurpose.
A bright tungsten bulb with a colour temperature of around 3400K that is sometimes used in portrait studios. Most studio photographers prefer the convenience of electronic flash.
A flashgun that has a circular electronic tube that is positioned around the camera lens or on the filter thread. It’s used in macro photography to produce an even distribution of light while fashion and still-life photographers create interesting halo shadows around the subject.
The sync socket on a camera that triggers an attached electronic flash at the precise moment when the shutter is fully open.
An electronic flashgun feature that allows the flash coverage to be adjusted. Flashguns are usually designed to cover the same angle as a standard lens, so when a wide angle lens is used you may find the edges of the frame are darker. A zoom head pulls closer to the flashtube to widen the angle and extends to throw the flash light out at a more concentrated angle.