Black point
From The Glossary of Digital Photography
The darkest point in an image. Typically, this should be pure black, with the three colors—red, green, and blue—equaling 0 (RGB=0,0,0). The black point can be seen by opening an image in Photoshop and looking at the histogram in Levels. The farthest point on the left of the curve is the black point. The placement of this black point can be adjusted with the black point slider just underneath the curve.
