Two components of photography that are directly dependent that a photographer must understand are flash and red-eye. The reason so many commercial cameras with flash give us a picture that makes us look like red-eyed demons is because of where the flash is put. When the flash is put directly above the lens, or beside it, like that, it is basically at eye level. This means the light goes into our eyes, and reflects off our blood vessels in the eye.
This is what you see when you get a red-eyed picture. To get this effect to go away, the flash has to be further from the subject. Usually, it has to be higher than the subject. Ever wonder why the lighting takes so much work in a photoshoot? This is why; they’re avoiding red-eye.