What exactly is plein air painting? Plein air is a term derived from the French phrase "en plein air," which literally means “in the open air” and is particularly used to describe the act of painting outdoors, which was originally developed by the Barbizon School and the Impressionist movement of the late 1800s.
En plein air : is a French expression which means "in the open air.” The term particularly refers to the act of painting outdoors rather than in a studio. Artists work quickly to capture their subject in natural light. The term is sometimes incorrectly applied to landscapes painted in the studio which employ such a direct technique that they seem to have been done out of doors.
Plein Air Painting: A painting done outside rather than in a studio. The term comes from the French en plein air, meaning 'in the open air'. The Impressionists were particularly interested in the influence of changing light outdoors on color.