Luncheon of the Boating Party by Pierre-Auguste Renoir.

As one of the fellow founders of Impressionism, Renoir was a good friend of Monet??. In the late 1860s, through the practice of painting light and water en plein air (in the open air), he and his friend Claude Monet discovered that the color of shadows is not brown or black, but the reflected color of the objects surrounding them. 

Included in the Seventh Impressionist Exhibition in 1882, 'Luncheon of the Boating Party' was identified as the best painting in the show by three critics. It was purchased from the artist by the dealer-patron Paul Durand-Ruel and bought in 1923 (for $125,000) from his son by industrialist Duncan Phillips, who spent a decade in pursuit of the work. It is now in The Phillips Collection in Washington, D.C. It shows a richness of form, a fluidity of brush stroke, and a flickering light.

The painting, combining figures, still-life, and landscape in one work, depicts a group of Renoir's friends relaxing on a balcony at the Maison Fournaise restaurant along the Seine river in Chatou, France. The painter and art patron, Gustave Caillebotte, is seated in the lower right. Renoir's future wife, Aline Charigot, is in the foreground playing with a small dog, an affenpinscher; she replaced an earlier woman who sat for the painting but with whom Renoir became annoyed. On the table is fruit and wine. The diagonal of the railing serves to demarcate the two halves of the composition, one densely packed with figures, the other all but empty, save for the two figures of the proprietor's daughter Louise-Alphonsine Fournaise and her brother, Alphonse Fournaise, Jr, which are made prominent by this contrast. In this painting Renoir has captured a great deal of light. The main focus of light is coming from the large opening in the balcony, beside the large singleted man in the hat. The singlets of both men in the foreground and the table-cloth all work together to reflect this light and send it through the whole composition.