Flash Units in Digital Photography

By Dan Feildman

Flash units can come in many sizes and shapes for digital photography. Those cameras on the lower end of the scale come with low energy built in flash units. However, some gear such as the high end digital SLR cameras can accommodate external flash units advanced in their abilities to provide excellent lighting in complicated situations. Know the basic facts about the difference between built in and external flash units.

In the early days of photography, flash units were much different indeed. They once consisted of powder that was lit by an electrical current and then literally "blown up" to produce a flash of light energy. This method was both dangerous for the photographer and difficult to manage as the flash units were not automatically designed to go off at the exact moment as the camera's shutter. The task of ensuring the two went off together rested on the photographer.

Today flash units have eliminated this challenge. An electronic flash tube ensures flash timing is synchronized to the camera. The photographer now gets to concentrate on other aspects of the photo. New digital cameras can even determine on their own if the flash is even needed, set its intensity and other parameters and fire the flash at the precise time the shutter is opened. All of this is automatically done in the background. Should the user want to make their own adjustments, digital cameras also allow the user to manually control the flash, set its intensity and more.

Flash units are divided into two categories: Internal built-in flash units or external flash units. Internal flash units are built into the camera. Almost all digital cameras include such a unit and allow the user some control over it through the camera's menus and buttons. External flash units are attached to the camera's body through a dedicated slide-in slot or by using an electrical cable. Not all digital cameras support external flash units. Usually the lower end pocket cameras do not allow external flash units while all high end digital SLR cameras do allow such external flash units. External flash units can vary a lot. They can have different light energy levels that they can emit and different mechanical characteristics. Some external flash units also include smart sensors to measure ambient light, distance and other optical parameters in order to optimize the flash effect.

Flash units can be used in both automatic and manual mode in most digital cameras. When in automatic mode, the camera measures ambient light and fires the flash when there is a lack of enough light. There can be times the camera will make the incorrect choice in using the flash and will either fire or not fire the flash when the contrary was needed. Setting the flash intensity is important also. Should the flash unit fire too much light energy on objects that are too close to the camera the digital photo will be washed out. Of course if the flash unit fires a small amount of light energy on an object that is farther away from the digital camera the digital photo will be a too dark.

Your flash unit does come with boundaries. They can not light every object and every scene at every distance from the camera. Know what you camera's flash unit limitations are. Experiment with different setups and determine what the highest light energy it can emit is and at what distance an object can be effectively lit from. This is called the effective flash range. Turn off the flash completely and use a tripod with a longer exposure if the object is out of the effective flash range. Should certain areas of what is considered a well lit scene still be dark, you might find it helpful to use the flash. This is known as fill-in flash and will fill-in the shadowed areas on objects in your photograph.

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