As a photographer your "paint" is light and how to control it to your advantage.
Most consumer DSLR's are equipped with a "pop up" flash. And this does serve its intended purpose. The in camera flash is good for fill in and adequate for occasional use.
The problems with most "pop up" flashes are that they lack real power, are mounted too close to the lens and due to the close relationship to the axis of the lens, cause "red eye".
Since a studio type flash system is both expensive and not very portable a hot shoe mounted flash unit becomes a great alternative.
Most offer good power and as they sit farther away from the axis of the lens they tend to lessen the "red eye" effect and shadows caused by the lens itself.
Many of the better quality hot shoe mounted flashes also include the ability of the flash head to be tilted up and to be rotated, allowing the user to bounce the light from the flash.
I recently picked up a Metz 48 AF-1.
Equipped with a USB port for firmware updates via Internet, it has shown itself to be just as innovative as its big brother the 58 AF-1 digital, which has just been singled out as “Europe’s Flash Unit of the Year 2007/2008”. Perfectly matched to digital cameras from leading manufacturers in each case, it is available in five different versions (Canon, Nikon, Olympus/Panasonic, Pentax/Samsung or Sony Alpha) – each individual one is flash-ready, due to its fully automatic flash modes. They facilitate precision light output, tailor-made for each individual subject. Numerous manual intervention options complement the photographic creative flexibility. Supported by a fully swiveling reflector system, which also has an extendable reflector card and a diffuser, almost unlimited possibilities open up for creative directed lighting. Thanks to the slave function, the 48 AF-1 digital can even be used detached from the camera. In the respective camera-specific wireless TTL mode, it can thus be used as a slave unit. It is an outstanding flash unit for committed amateur photographers.
I have much to learn as I begin to use the flash unit. So far, I am very pleased with it.