by Dan Feildman
Flash units will come in many different shapes and sizes in the world of digital photography. Those cameras on the lower end typically come with built in flash units. High end digital SLR cameras can accommodate sophisticated external flash units. These units can provide maximum lighting in difficult situations. Knowing the facts about flash units and their capabilities, both built in and external are important.
Flash units came a long way since their early days. Back then flash units were using powder that was lit by electrical current and literally “blew up” to produce the light energy. Using these flash units was a risky business. It was also difficult as the flash units were not automatically synchronized to the camera’s shutter. The photographer had to make sure that the flash goes off at the exact right time synchronized with the shooting of the photo.
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 separated into two basic categories: Internal built-in flash units or external flash units. Internal flash units are naturally built into the camera. Nearly all digital cameras come with such a unit and permit 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 can support external flash units. Generally the lower end pocket cameras do not support external flash units while all high end digital SLR cameras will. There can be quite a bit of difference in external flash units. 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 make the most of the flash effect.
Digital cameras can use their flash units in automatic or in manual mode. In automatic mode the camera measures ambient light and fires the flash when not enough ambient light is available. Sometimes the camera will make the wrong decision as to using the flash and will either fire or not fire the flash when the opposite was needed. Setting the flash intensity is important too. If the flash unit fires too much light energy on objects that are too close to the camera the digital photo will be washed out. On the other hand 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.
Flash units have limitations too. They can not light any scene and any object at any distance from the camera. It is important to know your flash unit limitations. For example check what the maximum light energy that it can emit is and what the farthest that an object can be effectively lit from. This is also known as the effective flash range. If the object is out of the effective flash range it is actually better to turn off the flash altogether and use a tripod with a longer exposure. Sometimes it is useful to use the flash even if there is enough ambient light. In such cases you can manually force the camera to fire the flash. This is also known as fill-in flash as it is usually used to fill-in shadowed areas on objects in the digital photo.
Source: Photography
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