I have a Canon Xsi. I am wondering what major purpose an external flash serves. I hate pictures where you can tell the flash was on by the extreme shadow in the background. However, I am needing a better lighting system for portraits (without the umbrellas and big equipment). I shoot people exclusively outdoors and sometimes half their face is hidden from the natural light. Here is an example: What specific external flash or accessories would you recommend? What is the difference between dedicated and non-dedicated flash? Thanks!