Basically, if the dynamic range of the scene is larger than the dynamic range of the camera, you need to use HDR to get a good image. Maxxx, I'm sure you've taken a pic where the sky is washed out or appears brighter than it actually is. Just go out and take a picture of the sunset, or at night and you'll see what I mean. This is where HDR helps in capturing the image. For example, that Tokyo shot would've been impossible to get without taking multiple shots.