Compact digital cameras are popular due to their small size and cost. Some advanced compact digital cameras are equipped with a hot shoe. A hot shoe is a mounting point on the camera that allows a more powerful external flash to be attached. A modern external flash consists of a xenon tube to emit light, capacitors to store electrical energy, batteries to charge the capacitors, a zoom head to help direct light, and an electronic circuit to allow the use of different flash outputs automatically or manually. When a flash is turned on, the batteries charge the capacitor until it is full and a ready signal is displayed. When given the command to fire, the capacitor releases its stored energy very quickly into the xenon tube, which emits a short burst of bright light.

Exposure is the total amount of light recorded by the digital camera’s image sensor. An image sensor is the digital equivalent of photographic film.  Exposure affects the brightness of the resulting picture and thus achieving correct exposure is very important. Correct flash exposure involves several factors including flash output, flash distance to subject, flash zoom, camera aperture, and ISO. Several combinations of these factors will all give the correct exposure because they are related through stops. Adding one stop of exposure doubles the amount of light received by the image sensor.

High speed flash exposure is the use of flash with high shutter speeds. It is a valuable feature to photographers because it allows the application of certain photographic techniques such as stopping fast motion and using fill light to reduce the contrast of a scene.

When a flash is mounted, the camera recognizes it and does not allow shutter speeds higher than the manufacturer’s specified maximum sync speed which is usually 1/250 second. The camera can be fooled into thinking that there is no external flash attached by blocking all but the centre trigger contact with a thin plastic chip so that all shutter speeds can be used. However, a certain amount of flash output may be clipped off. Clipping means the shutter will close before the discharge of flash is complete and thus only part of the discharged light is exposed onto the image sensor. Knowledge of the clipped flash output allows the use of flash predictably.

The objective of this project is to develop a technique to allow the correct use of flash at shutter speeds higher than the maximum sync speed.