Integrity of the picture plane A well-known phrase has accompanied many discussions of painting during the period of modernism. Coined by the influential art critic Clement Greenberg in his essay called "Modernist Painting", the phrase "integrity of the picture plane" has come to denote how the flat surface of the physical painting functions in older as opposed to more recent works. That phrase is found in the following sentence in his essay: "The Old Masters had sensed that it was necessary to preserve what is called the integrity of the picture plane: that is, to signify the enduring presence of flatness underneath and above the most vivid illusion of three-dimensional space." Greenberg seems to be referring to the way painting relates to the picture plane in both the modern period and the "Old Master" period. See also Image plane Perspective projection Projection plane References James C. Morehead Jr. (1911) Perspective and Projective Geometries: A Comparison from Rice University. Perspective projection