Conference paper. On the preproduction & production of the film Tosca (1939-1941), directed by Jean Renoir but finished by his assistant Carl Koch. Recently, I rediscovered a collection of over 200 photos of the location hunting for this film, made by Federico Patellani. The photos help define the style of Renoir's original project, but also hint at Patellani's famous postwar 'neorealist' photography. Intrinsically, the research reveals stylistic links between Renoir and his assistant for this film, future film director Luchino Visconti.