Marie-Christine Roux by Nadar
According to Helmut Gernsheim, Parisian photographer Nadar's photograph of actress Marie-Christine Roux unmistakably reappears in Ingres’s La Source. Helmut Gernsheim says that Ingres had sent Roux to Nadar for preliminary studies for La source, the same year the painting was completed.
The production of generic photographic nude studies, intended for art students as well as the public at large, were euphemistically called académies. They were many times cheaper than working with a real model. Noël Paymal Lerebours supplied the first ‘académies' as early as summer 1840. —Creative Photography: Aesthetic Trends, 1839-1960 by Helmut Gernsheim
Her body seems to display signs of corsetting. See in comparison this photo