Cheng Huan is so saintly because D.W. Griffith knew there was a lot of Sinophobia in the US, and audiences would have trouble accepting a Chinese hero. In the original short story, Cheng Huan is just a guy who joined the Chinese merchant marines when he got into debt, grew tired of shipboard life and ended up in Limehouse, a multi-cultural port district in the poor section of London. He was never a Buddhist missionary or a pacifist, and fell just short of being a statutory rapist (albeit, he really loved Lucy); another part of rehabilitating his character was to change Lucy's age from 12 to 16. The audience is not supposed to think they had a sexual relationship, but if people played that out in their heads, it wasn't illegal (unless it was under US miscegenation laws, but Griffith kept the London setting). Anyway, it wasn't child-rape. In the original story, the only way in Cheng Huan he is morally superior to anyone else is his ahead-of-its-time compassion for Lucy. Griffith's personal copy of "Limehouse Nights", the book with the short story "The Chink and the Child"--on which this film is based--with all his screen writing marginal notes, still exists, in a rare book collection at the Lilly Library on the campus of Indiana University, along with a manuscript copy of the story by the author, with comments by Griffith and Lillian Gish.
The only makeup Richard Barthelmess used in order to appear Oriental was a very tight rubber band stretched around his forehead, pulling his facial features slightly upward. The rubber band was cleverly concealed beneath his cap.
While filming the closet scene, Lillian Gish's performance of pure terror was so realistic that D.W. Griffith was compelled to shout back at her and urge her further. A passerby heard this going on and, convinced that something terrible was going on, had to be restrained from entering the studio.
The film's premiere engagement included a live prologue featuring a dance routine performed by actress Carol Dempster. During Dempster's dance the stage was illuminated by blue and gold footlights. Later, during the screening of the film, a stagehand accidentally switched on those footlights and the movie screen tinted the film in an unusual way. D.W. Griffith, standing in the rear of the auditorium, was so surprised and delighted at the blue and gold-tinted effect that he ordered all copies of the film to be tinted in those colors during certain key sequences.
The failure of the original copyright holder to renew the film's copyright resulted in it falling into public domain, meaning that virtually anyone could duplicate and sell a VHS/DVD copy of the film. Therefore, many of the versions of this film available on the market are either severely (and usually badly) edited and/or of extremely poor quality, having been duped from second- or third-generation (or more) copies of the film.
The trivia item below may give away important plot points.
The film was produced by D.W. Griffith for Adolph Zukor's Artcraft company, a subsidiary of Paramount Pictures. But when Griffith delivered the final print of the film to Zukor, the producer was outraged. "How dare you deliver such a terrible film to me!" Zukor raged. "Everybody in the picture dies!" Infuriated, Griffith left Zukor's office and returned the next day with $250,000 in cash, which he threw on Zukor's desk. "Here," Griffith shouted, "If you don't want the picture, I'll buy it back from you." Zukor accepted the offer, thus making this the first film released by United Artists, the production company formed in 1919 by Mary Pickford, Charles Chaplin, Douglas Fairbanks, and Griffith. It was a remarkably successful film, both critically and at the box office.