In the market there are a considerable amount of external flash, of various brands, power, with different functions and especially with different prices. In addition to these built-in flash in the SLR are called pop-up (are all xenon lamps).
The flash is the cross and the delight of the photographer viscerally hated the internal flash of the photo machine and, on the contrary, loved the outdoors.
Photographer Scott Kelby, some time ago, gave a definition all the more perfect for the internal flash
built-in flash in the camera is designed for one purpose to create the flat light, unpleasant and hard that modern man has ever made http://bdmaster.net. If you have it with someone, take it back with the built-in camera flash, and the bill pareggerete
Kelby basically summarizes the few words what are the disadvantages of the pop-up flash
Assuming that the smaller the area of ??irradiation and harder is the light (as seen observing a flashlight – harsh light – and with a light bulb – soft light -), the pop-up flash emits a particularly harsh light being very limited as a dimension.
Because of the location (immediately above the lens), the light of the pop-up flattens flash photography (in fact they are also deleted most of shadows on our uniformly subject), by removing entirely or almost the dimensionality simulated with the use of shadows or lines.
The pop-up flash I have the unpleasant inconvenience (now corrected directly during shooting) to be reflected in the eyes of the subject this result will appear with the same red.
Being small in size, its scope is particularly limited, at most a couple of meters. Forget zoom or possibility to remove the person from your goal
In contrast, passing the outdoor unit, the advantages of the latter are more or less the disadvantages of the pop-up overturned flash
the light emitted by the flash is directable
the area of ??irradiation is significantly larger (depending on the flash in each case)
you can direct the light on the ceiling or on the walls in order to obtain the rebound effect (no direct lighting)
being much more top-mounted to the objective does not have a flattening effect (in the case of direct illumination) labeled and does not generate red eyes
We can control the flash output in a few moments and then better manage the situation
Its scope is greater, if we are always limited, in the case of powerful flash, about 5 meters.