Did you know that some of the most famous paintings by Van Gogh, Gauguin, Degas, and Toulouse Lautrec were based on photographs? While some impressionists and post-impressionists publicly disparaged photography as mechanical, many others were using it as their secret weapon. The relationship between the two arts was complex and intertwined. (And turning the tables, check out this contemporary Russian woman who is recreating several famous paintings in staged photographs.)Check out these photos.