Ch: yipin. Also ikkaku 逸格 (Ch: yige). Lit. the Untrammeled Class. A category or ranking of quality in Chinese painting and calligraphy. The Untrammeled Class exists in an ambiguous relationship with the more orthodox *sanpin 三品 or Three Categories. Chinese critics after the Northern Song set the ippin as a higher rank within the same critical framework. The term seems to have been coined by the Tang dynasty critic Li Suchen (Jp: Ri Shishin 李嗣真, late 7th century) and was originally applied to poetry as well as painting and calligraphy. Ippin generally implies an aberrant style of painting unrestrained by conventional rules, and is used to describe the sketchy rendering of form that spontaneously grasps the natural essence of visual phenomena.
Painting in the ippin style, ippin gafū 逸品画風, flourished from the late Tang (9th century) to the early Yuan (13th century), particularly in figure painting where it was favored by Zen 禅 (Ch: Chan) Buddhist artists. The painting of Two Patriarchs Niso Chōshin-zu 二祖調心図 (Tokyo National Museum) a close copy after Shi Ke (Jp: Seki Kaku 石恪, active mid-10th century), is a well-known work of this type. The ippin style also is seen in landscape, as illustrated by the paintings of Mi Fu (Jp: Bei Futsu 米芾, 1051-1107) and Yujian (Jp: Gyokukan 玉澗, active mid-13th century). Because ippin painting denied the necessity of close fidelity to perceived objects it can be seen as a key concept behind expressive painting of the Song and later periods, as well as influential in developments in Japanese ink-painting *suibokuga 水墨画.