She starred in The End of the World, which was screened in the Un Certain Regard section at the 1993 Cannes Film Festival.
The film premiered in Cannes 2008, where it opened the official sidebar section, Un Certain Regard and would go on to win the Golden Camera award (Camera d'or).
Its first official screening was at the 2009 Cannes Film Festival where it won the Special Jury Prize Ex-aequo in the Un Certain Regard section.
Firth gained international acclaim as the older of two sisters vying for the attentions of a lecherous DJ in Shirley Barrett's Caméra d'Or winning debut, Love Serenade, screening in Un Certain Regard at the 1996 Cannes Film Festival.
Her film Marcello Mastroianni: mi ricordo, sì, io mi ricordo was screened in the Un Certain Regard section at the 1997 Cannes Film Festival.
His film Cóndores no entierran todos los días was screened in the Un Certain Regard section at the 1984 Cannes Film Festival.
Voices of Sarafina! is a 1988 American documentary film directed by Nigel Noble about the anti-apartheid musical stage play Sarafina! It was screened in the Un Certain Regard section at the 1989 Cannes Film Festival.
"No One Knows About Persian Cats" (2009) feature film directed by Bahman Ghobadi, which won an Un Certain Regard Special Jury Prize Ex-aequo at the Cannes Film Festival.
Recent roles include starring opposite Armand Assante in California Dreaming which won the Un Certain Regard award at the 2007 Cannes Film Festival; portraying a young Sigmund Freud, again opposite Assante and Ben Cross, in When Nietzsche Wept; and on the small screen, where he improvised with Larry David in HBO’s Curb Your Enthusiasm.