ZoneFinder
By default when editing a photo, in the upper-right corner of the LightZone window is the ZoneFinder that shows a miniature version of your photo that has been segmented into 16 grayscale zones each differing by 50% brightness or half an exposure value (or half an f-stop) from the next.
The ZoneFinder allows you to see where the highlights, midtones, and shadows in your photo are in order to make adjustments using the ZoneMapper tool.
The ZoneFinder is based on the Zone System.