One of the biggest factor that affects the quality of a photograph is the lighting. The position of the light source relative to the subject, the amount of light available, the color (hue) of light, and how light bounces around a scene determines how good or bad your pictures could look.
To a certain extent you can adjust the camera's Aperture, Shutter speed, or ISO appropriately to tune the amount of available light that should illuminate the subject. However, you cannot control the direction of the light or how the light is scattered by the various surfaces in the scene causing all sorts of highlights and shadows. Of course you can always move your subject or shoot at an angle where the current lighting will produce nice shadows and details on your subject, however you will lose control over the background and overall scene that you want to capture.
If you are using RAW, with a little Post Processing using various photo-editing software, you can probably achieve certain degree of correction on the exposure, shadows, highlights, hue, etc., but, in extreme cases, due to the limitation of the hardware and current camera systems, there are usually unwanted side effects that are difficult if not impossible to control, such as noise, banding, or loss of detail.
A bigger headache would be shooting in a scene with various colored light sources (direct, reflected or refracted) such as in a church with stained glass windows. This causes your camera's white balance to produce unpredictable results. If you're lucky the result could be quite pleasant, but, in most cases this could force you to end up converting your photos to black-and-white.
Flash Photography and the use of artificial light sources is a way of compensating for the inadequate available light in a scene or simply to manage the lighting to produce a more controlled and well-balanced scene to suit the photographer's taste or to produce a certain effect.
Using a Flash or a Flash system, however, is not a simple all-in-one magic solution to your lighting needs. Whether you use the built-in flash or use a single external flash or a complicated set of remote controlled flash system, there are a few basic things that you first need to understand in order to properly optimize the use of your setup.
Read through the basics of Flash in the next pages and how it affects your photos. Learn what things to look out for and what to avoid. See how you can control Flash and make the best of whatever setup you are using. There are also some tips I have gathered to allow you to do simple tweaks or add simple accessories to your current setup to improve the results of your photos with flash.