San Francisco’s Museum of Modern Art’s Chief Conservator, Will Shank, always beliebed there was another painting hidden under Pablo Picasso’s “Scene da Rue”. To the naked eye, some of the colors don’t match up. Also, some of the bushwork seems at odds with the final product.
With modern technology they had a way to find out. First, they took high definition digital photographys of the painting. They colors showing through the cracks was transferred to a black and white radiograph. They used a binocular microscrope to see the out of place colors and recreated the original painting.
Picasso was known for painting over paintins. It was a sort of game with him. a 1956 film shows him tranforming one painting into another into another.
You can see how the painting was reconstructed at http://www.sfmoma.org/hiddenpicasso