American School (20th century), California Plein Air Landscape, oil on canvas, unsigned, canvas: 24"h x 30"w, overall (with frame): 29.5"h x 39.5"w Again an excellent example of the California Plein Air movement at the turn of the 20th Century, Clean and grime free without damage nor repair and framed in a period arts and crafts frame. En plein air painter on the Côte d'Argent in Hourtin, France En plein air (pronounced [ɑ̃ plɛ.n‿ɛʁ]; French for 'outdoors'), or plein-air[1] painting, is the act of painting outdoors. This method contrasts with studio painting or academic rules that might create a predetermined look. The theory of 'En plein air' painting is credited to Pierre-Henri de Valenciennes (1750–1819), first expounded in a treatise titled Reflections and Advice to a Student on Painting, Particularly on Landscape (1800),[2] where he developed the concept of landscape portraiture by which the artist paints directly onto canvas in situ within the landscape. It enabled the artist to better capture the changing details of weather and light. The invention of portable canvases and easels allowed the practice to develop, particularly in France, and in the early 1830s the Barbizon School of painting in natural light was highly influential.[3] Amongst the most prominent features of this school were its tonal qualities, colour, loose brushwork, and softness of form. These were variants that were particularly relevant to the mid 19th-century Hudson River School and to Impressionism