Widely regarded as the greatest of the Impressionist painters, Claude Monet's loose set, or series, of paintings of haystacks at different times of the day is classified as painting en plein air (b).
In fact, taking the canvas outdoors is among the notable achievement of Impressionism, and Monet was most dedicated to recording the impression of the moment, be it sunrise or sunset. One year in Giverny, Monet was attracted to the sight of haystacks being built up in the fields. And, on one particular day, the light changed so quickly that he sent his stepdaughter running to the house for one canvas after another as he recorded these changes on the hay field, thus creating his series of haystacks. While these paintings exhibit a certain homogeneity, they are distinguished by the play of light and the atmosphere which envelops them.
Monet's contemporaries were most struck by the execution of these paintings entirely outdoors--en plein air--in a most natural manner as not a single brush stroke was added in the studio later. The Haystacks paintings mark an important step away from the tradition of painting subjects that were affecting or entertaining or informative. Indeed, they are objects in their own right, rather than a mirror held up to nature. For the first time, too, viewers felt the emotional charge of unadulterated color in the play of light upon objects as the prime objective of the artist.