Flash photography

When  the available light is not enough for correct exposure a flash is often used. The flash light uses a bright bulb to temporarily light up the surroundings, just long enough to take the photograph.

The shutter speed must be set at the camera’s designated flash synchronization speed, often 1/125 of a second, or lower. If a higher speed is used only partial exposure of the frame will result. The amount of light falling on the subject reduces at a very fast rate the further you are away from the subject. use of the more powerful off-camera flashes is recommended as the built-in flashes tend to have a much lower output and are only really useful for snapshots. 

Read the manual for your flash since flash units vary considerable in features and the degree of automation that is possible. Many modern flash units are dedicated to particular camera models and will function as an automated extension of the camera, ie  Canon Speedlite 580Ex on an EOS 1D mkII, this means you maintain full TTL (through the lens) metering.

Flash is also very useful for adding fill light into shadows, particularly when photographing in full sunlight. Again the sync speed must not be exceeded but many of the dedicated flashes (see above) can be set for fill-in flash and makes life much easier. This is also a good technique for backlit subjects to even out the exposure over the whole frame.

It’s advisable to use the flash gun at an angle inclined to the subject and shining a flash gun directly at the subject should be avoided. Not only can it cause damage to the eyes of the subject but will also produce a reddish tint in the eyes of the subject, commonly called the ‘red-eye’ effect caused by the light reflecting from the blood vessels in the rear of the eye. Flash can be 'bounced' from reflected surfaces such as ceilings or reflectors to provide a soft diffused light for flattering portraits and avoidence of red-eye.

 The correct use of flash is an art form in itself and there are many photographers who specialise in flash photography using flash in very creative ways to produce stunning results. This area is often overlooked and doesn't come to the photographers attention until he has a set of incorrectly exposed prints to deal with. Like anything else seek advice and practice the use of flash, even if you only use basic flash functions, your pictures will benefit and you may discover a whole new world. 

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