Flash photography is available for more than a century. In the beginning flash photography was available only to the professional and skilled photographers. The old flash units were very hard to use. They utilized a chemical that would literally blow in order to generate the needed light. They were also disposable units and had to be completely changed after each use. Moreover they were not automatically synchronized to the camera shutter and thus the photographer had to be skilled in perfectly timing the flash unit with the camera shutter. Modern cameras and moreover digital cameras use electronic flash units that are automatically synchronized with the shutter and that use a special electrical device for lighting the scene that can be over and over.



Flash photography is different than regular day light photography. There are many things to consider when using flash, here are a few:

Built-in flash units: Built-in flash units are embedded in the camera and controlled through the cameras interface. Built-in flash units are thus small as they have to fit inside the camera body. They are also designed to be as generic as possible to meet all the different scenarios the camera might be used in. They are also limited in their illumination capacity and can be used only when taking photos of relatively close by objects. On the advantages side built-in flash units are very easy to use and carry they do not require any extra accessories, batteries or maintenance. External flash units on the other hand are harder to use but provide more coverage in terms of object distance and more flexibility for usage. For example built-in flash units do not allow effects such as bounce flash while external flash units do. The Canon 48AF-1 on the other hand is an external flash unit and is normally used by semi professional or professional photographers. It works with any Canon compatible camera.

External flash units: The Canon 48AF-1 is an external flash unit. The external flash slides into a mechanical slot on the camera. The slot also has electrical connection built into it and thus the flash unit is electrically connected to the camera micro-computer. The Canon 48AF-1 like other Canon external flash units connects to the cameras micro-computer and is completely controlled by it. The camera micro-computer takes care of shutter synchronization other optical settings that need to be synchronized between the camera and the flash unit.

Firing the flash: Both built-in and external flash units can be fired either manually or automatically. In automatic mode the camera measures the ambient light and based on that and other optical factors and settings decides if firing the flash is needed or not. Although in most cases the camera can make the right decision as to whether or not the flash is needed many times it will fire the flash when it is better not to and vice versa. An example of such a case is when taking a photo at day light but having some shades over the object for example a man wearing a hat can result in shades over the man's face. In such a scenario although there is enough ambient light using the flash in fill-in mode would eliminate such shades and result in a much better digital photo.

Flash has limits: Flash units can only do so much. They can not light a big area for example and are limited to how far an object can be from the camera in order to be properly lit. Different flash units have different limits. Usually built-in flash units are weak and can only illuminate objects that are a few feet a way from the camera. On the other hand external flash units can illuminate object much farther away.