most impressionist landscape paintings are small, so that the artist could carry them outdoors. some artists, particularly claude monet, would take several canvases, and as the day went on and the light changed, he would put down one and take up another. he rented a room from which he could see rouen cathedral so that he could paint it from the window at different times of day. monet also did a series of "haystack" paintings, showing them standing in the field from different angles and in all sorts of weather, bright sunshine, morning frost and snow. paintings that are done outdoors are called "plein air" paintings. the impressionist painters often used to go out together on painting trips, so there are many pictures that can be compared.