Meaning of zone system

zone' sys"tem

Pronunciation: [key]
— Photog. Photog.
  1. a system for envisioning the values to appear in a black-and-white print and for determining exposure and development, based on a scale of shades ranging from 0 (black) to IX (white).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.