Home Online catalogues True to Nature. Open-air Painting 1780-1870 11. Pierre-Henri de Valenciennes Toulouse 1750 – 1819 Paris Study of a Tree in the Bois de Boulogne, c. 1790 A pivotal figure in the development of landscape painting, Valenciennes effectively elevated its status through his promotion of the paysage historique. In his work as a painter, teacher and author, he advocated that such composed landscapes should be based on the direct study of nature. His treatise Élémens de perspective, published in 1799/1800, laid out guidelines for artists who wished to paint out-of-doors and was still considered essential reading for Camille Pissarro in the 1860s. Informed by his experiments painting en plein air in Italy and France, Valenciennes recommended that sessions last no more than two hours to ensure consistency in the rendering of light, colour and atmosphere. He encouraged his readers to make painted studies of trees in isolation or in groups, faithfully recording details of the bark, moss, branching, roots and, especially, foliage. The author did stress, however, that these studies were not paintings in themselves, but that they should be kept in portfolios and consulted as aide-mémoires when needed. In his own study painted in the Bois de Boulogne, Valenciennes presents the tree from a low-angle view, giving it a certain monumentality while isolating it from the rest of the forest, only lightly sketched in the background.