Lighting ratios are one of the principles every photographer who uses off-camera flash doesn’t think they’ll need, but in reality makes their life much simpler once mastered and practiced. The most famous use of lighting ratios has to do with making a white background go totally white.
In general, it helps you figure out what an image will essentially look like and how much power needs to be produced from each light in your scene.
Dan over at AdoramaTV did a tutorial on lighting ratios and for some of us, it will help to get a specific creative vision across. This may be very subtle but in reality it’s actually quite a bit of light loss when presented in the succession that is shown in the video. Shadows in an image can give off a much different feeling vs a totally shadowless image; and that’s really what lighting ratios are all about.