The third type of painting associated with Ch'an is the monochrome landscape. Landscape was not originally a major Ch'an subject, but Ch'an monks experimented with the traditional Chinese treatment of such scenes and so influenced Chinese landscape painting that even academic paintings during the Sung dynasty reflected the spontaneous insights of Ch'an philosophy. Landscapes represent Chinese painting at its finest, and the Japanese Zen painters who embraced the form made it the great art of Zen. The technical mastery of landscape painting had been achieved late in the T'ang dynasty when the problems of perspective, placement, and vantage point were solved. The classic rules for the genre, which were formalized during the early Sung dynasty, were respected for several hundred years thereafter in both China and Japan. One must appreciate these rules if one is to understand the Far Eastern landscape. To begin with, the objective is not photographic accuracy, but a representation of an emotional response to nature, capturing the essentials of a landscape rather than the particular elements that happen to be present in a single locale. (In fact, Japanese Zen landscapists frequently painted Chinese scenes they had never seen.) Nature is glorified as a source of meditative insight, and the artist's spontaneity is expressed within a rigid framework. Certain specific items are expected to appear in every painting: mountains, trees, rocks, flowing water, roads, bridges, wildlife, houses (or at least thatched huts). The mountainsides vary with the seasons, being lush and sensuous in spring, verdant and moist in summer, crisp and ripe in autumn, and austerely bare in winter. The tiny human figures show the dignity of retired Sung officials at a hermitage; there are no genuine farmers or fishermen. The paintings have no vanishing point; receding lines remain parallel and do not converge. The position of the viewer is that of someone suspended in space, looking down on a panorama that curves up and around his range of sight. To depict distances extending from the immediate foreground to distant mountain ranges, a painting is divided into three distinct tiers, each representing a scene at a particular distance from the viewer. These include a near tableau close enough to show the individual leaves on the trees and ripples on the water, a middle section where only the branches of three trees are delineated and water is usually depicted as a waterfall, and a far section containing mountain peaks. Since these three levels represent quantum jumps in distance, fog or mist is often introduced to assist in slicing the painting into three planes. These landscape conventions were the subject of volumes of analysis and interpretation during the Sung dynasty. According to the painter Han Cho in a work dated 1121: