Sharing space with the
ZoneFinder,
Color Selection Viewer,
and
Sampler
in the upper-right corner of the LightZone window
is also the histogram
that shows the distribution of intensity
for each of the red, green, and blue color channels.
For example, the histogram in the upper right shows that the photo has little contrast (because none of the color channels extend into the darker zones) and is also slightly underexposed (because none of the color channels extend into the lightest zone).
The histogram in the lower right shows the same photo after both exposure and black point adjustments have been made using the ZoneMapper tool. Notice how the color channels now extend all the way from the darkest zone to the lightest.