He directed over 30 films over the course of his career including such well known (and respected) movies as "Jeremiah Johnson," "Tootsie," "The Way We Were," "Three Days of the Condor" and "Out of Africa." He also made many appearances in film, usually in a comedic role. I think he's best known for his role in the movie "Tootsie" which starred Dustin Hoffman as an actor so desperate to land a job that he impersonated a woman. Sydney played Dustin's agent in the film.
He may be better known to younger folks as the guy in the "don't talk on your cell phone" promotional short that plays ahead of many movies where he tells a guy "I'm sorry, is my directing interrupting your phone call?"
He always seemed to me to be a genuine guy and I know he will be missed.
My condolences to his family and friends.