Monday, July 28, 2008

Flash Units in Digital Photography

By Dan Feildman

Digital cameras flash units come in many shapes and sizes. Low end digital cameras include low energy built in flash units. High end digital SLR cameras can support sophisticated external flash units which can provide superior lighting in difficult scenarios. Here are some basic facts about flash units both built in and external.

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.

Nowadays flash units are sophisticated technology devices. They use an electronic flash tube that is automatically synchronized to the camera. The photographer merely needs to do nothing. New digital cameras can decide on their own if the flash is needed, they can set its intensity and other parameters and they can fire the flash at the exact right time when the shutter is opened. All this is done automatically in the background. Digital camera also provide the user with the ability to manually control the flash, force it to either fire or not to fire, set its intensity and more.

Flash units are separated into two categories: Internal built-in flash units or external flash units. Internal flash units are built into the camera. Most digital cameras include such a unit and let the user have some management 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. Typically the lower end pocket cameras do not allow external flash units while all high end digital SLR cameras do allow external flash units. External flash units can differ greatly. They can have different mechanical characteristics and different light energy levels that they can emit. Some external flash units also include smart sensors to measure ambient light, distance and other optical parameters in order to get the most from the flash effect.

Both automatic and manual flash unit modes are made available on digital cameras. In automatic mode the camera measures ambient light and fires the flash it deems not enough ambient light is present. There can be times the camera will make a mistake in using the flash and will either fire or not fire the flash when the opposite was needed. Keep in mind the importance of setting the flash intensity. 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. 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 then 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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