It was there that he developed his long-term essay of the life of a Puerto Rican family in Spanish Harlem, for which he won the Yann Geoffroy Prize in Milan in 1990.

[26][18] He won the King Albert Memorial Foundation Prize[27] in 2000 for his book on Swiss mountain farmers (Bauern am Berg, Paysans de nos montagnes, Vita di montagna).

In 2000 and 2001, Ruef was commissioned by the Swiss branch of Médecins Sans Frontières (MSF) for an extensive photographic report on daily life in six African countries.

In 2007, he was commissioned by the Swiss Foundation DiDé, Dignité en Détention, for a book Enfants Prisonniers[31] on the minors' jail in Gitarama, Rwanda.

He has shot twenty photo essays and has finally published in 2011 the book Recycle,[32][33] Labor et Fides (French-English) and Edizioni Casagrande (Italian-German).