Nowadays using flash photography is easy one push of a button and most cameras do everything for you. It was not always so easy. Flash is needed for example to take photos in dark scenes or to get rid of shades in fill in mode. We will look at general attributes of flash units and the Canon Speedlite 580Ex in particular.

Photographers have practiced flash photography for more than a century. In its early days it was a risky and a manually controlled technology. Flash used powder that was ignited by fire or electrical current. These flash units were both dangerous and very hard to use since the flash was not automatically synchronized to the camera's shutter. The photographer had to manually synchronize the shutter and the flash making sure that the flash was fired at exactly the time when the shutter was being opened. Nowadays new flash units use an electronic flash tube that is perfectly synchronized with the camera's shutter and are safe to use.

Here are some important subject when considering flash photography:

Internal flash units: These are built into the camera and controlled through the camera's menus and buttons. They are small as they are limited by the camera body size. Being small units they are usually weak and only allow usage to a distance of a few feet. They are very easy to use and carry around as they do not require any special settings or buying and installing accessories. The Canon Speedlite 580EX is an external flash unit and is normally used by semi professional or professional photographers. It can be used with any compatible Canon cameras such as the EOS, Powershot ad Rebel cameras. Apart from a few low end models that can not fit an external flash unit most mid and high end cameras to allow such units.

External flash units: the Canon Speedlite 580EX is an external flash unit. It is mechanically attached to the camera's body through a dedicated slide-in slot. It weighs about 13 ounces and its guide point is at 190 feet. The Canon Speedlite 580EX connects to Canon cameras micro-computer and can be fully controlled by it. It is automatically synced with the shutter and can also get feedback from light and other camera sensors.

Firing the flash:Firing the flash is either automatic or manual. The camera can fire the flash when there is not enough light available. Sometimes the camera will not automatically fire the flash though using the flash would have resulted in a much better photo. For example taking a photo during day time when the object is shadowed. In such scenarios using the flash in fill-in mode would light up the shaded areas and result in a better photo.

Flash is limited: Every flash unit is designed to be used within a specific distance from the object. If you take a photo with your objects not within the flash unit range it is better to turn off the flash completely and use a tripod and long exposure. Using the flash in such scenarios can fool the camera into setting lower exposure which results in a photo darker than a photo taken without using the flash at all.