Scientists recapture Renoir's reds
13 February 2014 Last updated at 22:16 GMT
Researchers in Chicago have produced a visualisation of how they think a Renoir could have looked before its colours faded.
The picture of Madame Valentine Clapisson was painted by the great French Impressionist more than 130 years ago.
The original's impact has been degraded and dulled by the action of light.
But by using the latest analytical tools, conservators have been able to recover a sense of Renoir's rich reds.
Dr Francesca Casadio from the Art Institute of Chicago describes the painting to our correspondent Jonathan Amos.