The phrase "en plein air" translates to "in open air". Most painters understand it to mean works done outdoors. Painters began to use this approach in the nineteenth century as a way of taking their subject directly from nature. It was employed by realistic painters working to capture their landscapes accurately, as seen in the French Barbizon School. It was also used by the Impressionists, who did not seek to record what their eyes were seeing, but what impressions they were getting from the interaction of light and shadow in the honest light of day, en plein air.
Unlike studio work, plein air painting presents new challenges to the artist who is asked to focus on the view in front of their easel. It also involves a more rapid performance on the part of the artist, since light changes as the day progresses and therefore their brushwork cannot be as considered or labor intensive as in the controlled environment of the studio.
One of the first proponents of the method was English landscape painter John Constable, who believed there was truth in nature. Almost at the same time the earliest Barbizon artists were drawing nearly the same conclusions, and painters such as John Francois Millet and Gustave Courbet were choosing to paint the landscape and its inhabitants as their subject matter.
Later the Impressionists would employ the method as a way of accurately documenting the play of color and light outdoors in nature. They would also frequently set their subjects in gardens or parks to use the play of light and shadow. For example, Monet is known for painting the water lilies of his gardens at Giverny under all times of day and through many season.
American artists as well took advantage of their native light, and the American Impressionists captured the remarkably diverse landscape in a variety of ways, with a majority looking to record their immediate view in its actual environment.