When it comes to filmmakers who indelibly impacted the medium, Orson Welles ranks right alongside D.W. Griffith, Alfred Hitchcock and the other innovators who shaped and formed cinema as we know it today.

Now's a great time to revisit the extraordinary big screen output of this iconic craftsman, who re-invented how movies worked in "Citizen Kane" and continued forging new territory thereafter. Film Forum offers quite the opportunity to do just that during a month long series -- running through Feb. 3 -- that celebrates Welles' 100th birthday.

These are some of the many highlights:

 

'Citizen Kane'

 

There have been countless books written about the impact and legacy of this movie, widely considered to be the greatest ever made, so it's hard to do it justice in just a few sentences. Let's just say that the late, great Roger Ebert noted that he'd experienced the story of newsman Charles Foster Kane, told brilliantly through intricate and unreliable flashbacks, experimental sound design and deep focus cinematography, at least 100 and always came away with something new. "Its depths surpass understanding," he wrote, and we couldn't put it any better. (Through Thursday)'The Magnificent

 

Ambersons'

 

Welles' follow-up to "Citizen Kane" had a bit of a tortured history, being re-edited by RKO against the filmmaker's wishes. It's still widely considered one of the best movies ever made, an adaptation of the Booth Tarkington novel about a Midwestern family experiencing significant social change at the start of the 20th century. (Friday, Saturday, Jan. 17)

 

'Touch of Evil'

 

Film Forum is showing three different versions of Welles' noir masterpiece, starring Charlton Heston as a detective, Janet Leigh as his fiancé and the director as the police chief in a film centered on the investigation into a car bombing on the U.S.-Mexico border. The opening long take is a characteristically virtuoso Welles filmmaking feat. ("Preview version:" Jan. 14, "Release version," Jan. 29, "1998 reconstruction," Feb. 1 and 2)

 

'The Lady from Shanghai' and 'The Third Man'

 

The theater is showing these noir classics on a double bill. "Shanghai" stars Rita Hayworth in one of her most famous parts opposite her husband Welles and "The Third Man" (directed by Carol Reed and co-starring Welles as Harry Lime) is well-known for its expressionistic sensibility and an iconic Ferris wheel sequence. (Jan. 23-24)

If you go:

Orson Welles 100 runs through Feb. 3 at Film Forum, 209 W. Houston St., 212-727-8110.