The earliest-known film from iconic British director Alfred Hitchcock screens in Los Angeles this week for the first time in more than 80 years - but it would have been lost if not for an eccentric hoarder half a world away in New Zealand.

The only known print of the 1923 feature The White Shadow lay in a garden shed in the North Island town of Hastings for decades, alongside hundreds of other films from the silent era.

The collection was assembled by Jack Murtagh, a cinema projectionist who New Zealand Film Archive chief Frank Stark described as a "magpie", unable to throw away the prints that passed through his hands.

Murtagh died in 1989 but his hoarding instinct has left a rich legacy for film buffs, including shorts, newsreels and features from the early days of Hollywood that were bequeathed to the film archive.

Researchers last year found the only surviving copy of a 1927 comedy called Upstream by American director John Ford - who went on to make Stagecoach, The Grapes of Wrath and The Searchers.

They struck gold again this year, uncovering the first three reels of Hitchcock's The White Shadow, the melodramatic story of two sisters, one angelic and the other a smoking, dancing rebel, seduced by the Parisian nightlife.

Hitchcock, who died in 1980, wrote the film's scenario, designed its sets, edited the footage, and was assistant to the British film director Graham Cutts, who bristled with professional jealousy toward the gifted upstart.

Stark said it was widely-regarded as Hitchcock's film, making The White Shadow and Upstream priceless opportunities for scholars to examine the fledgling efforts of two iconic filmmakers.

"They were both jumping off points for hugely important figures in world cinema," he said.

"Even blindfolded, (scholars) would still perceive an extra quality and dimension to these films.

"Here are outstanding examples of some genre-bending work in the very earliest days of production-line studio filmmaking."

Asked how such cinematic treasures wound up sitting in a New Zealand shed, 11,000km from Hollywood, Stark said there was a simple explanation.

He said in the early days of cinema, a limited number of prints were sent from Hollywood for overseas distribution and geographically isolated New Zealand was the final stop on the world circuit.

"When films reached here, they were deemed to be at the end of their distribution life," Stark said.

"No one had an archival impulse in those days. The assumption was that these were ephemeral ... they were of no value to anyone."

The standing order from the studios was to throw away the prints, Stark said, because it was not worth shipping them back to America.

He said that fortunately Murtagh and a handful of other film enthusiasts disobeyed, preferring instead to squirrel the reels away.

The archive was also lucky that the climate in Hastings is dry and mild, helping preserve the nitrate in the prints, a notoriously unstable substance that is highly flammable and degrades over time.

The three surviving reels of The White Shadow were warped and cracked when they were found, but in good enough condition for Peter Jackson's Park Road studio in Wellington to make a new print on modern film stock.

Park Road archive preservationist Lynne Reed, who said one of her fondest movie memories was being terrified during the infamous shower scene in Hitchcock's Psycho (1960), helped create the print.

She said Hitchcock's talent shone through as she worked on the film frame-by-frame.

"I realised what a genius he was at an early stage," she said.

"This was probably last screened in about 1930 and here we are 80-odd years later working on it. So it's a huge privilege."

Stark said most of Murtagh's films came from America and had been largely examined by researchers in recent years, but there was another cache of European films from other collectors and could also contain lost masterpieces.

"There's hundreds of titles, we don't have any idea what's in there yet," he said.

"There's every chance, extrapolating from the American experience, that there will be films that will be here and nowhere else."

Stark said Hollywood was fascinated when Ford's Upstream screened there last year and he expected the same reaction when the new print of The White Shadow debuts at the Academy of Motion Picture Arts and Sciences headquarters in Los Angeles on September 22.

He said Murtagh would have loved the attention his garden shed collection was receiving in the home of cinema.

"He was a projectionist, he loved Hollywood, he'd be thrilled he had made such an impact on Hollywood because Hollywood had such an impact on him," he said.

- AAP