A chemical smell hangs in the air at the British Film Institute's National Archive, where some 250,000 wheels of old film are stacked floor-to-ceiling.
"As we're restoring them we're pulling back the veils of history, and we can see much more clearly than we used to," curator Bryony Dixon told AFP on a visit to the archive in the town of Berkhamsted this week.
A selection plucked from the shelves is being showcased at the BFI's London Film Festival, including a tale about the heartbreaking Indian love story of the Taj Mahal mausoleum.
"It's beautiful, it's dramatic, it's got exciting locations, and great acting. And it's unique, there are almost no surviving Indian films from that era, so it's very special," Dixon said.
More From This Section
A score by composer Anoushka Shankar, daughter of late Indian sitar maestro Ravi Shankar, has also been added to accompany the silent film.
BFI curators have restored a wealth of films including Alfred Hitchcock's nine surviving silent films and footage of a legendary Everest expedition in 1924 in which two of the climbers died.
"There will be a lot of hand, manual repair on the original film copies, using tape to make sure the films can pass through cleaning machines, and also through the scanner," said Kieron Webb, the archive's film conservation manager.
The team used the original camera negative of "Shiraz", along with a copy made decades later, which were combined digitally to obtain the best images and restore tens of thousands of frames.
"The removal of scratches and dirt; de-flicker, which makes the image look more stable; reduce the light and darkness changes in some shots," said Webb, summarising hundreds of hours of work.
Restorers have also sharpened the images, which Thompson said creates more work: "As soon as you improve the sharpness of the image it reveals, brings into sharp focus the detail but also the defects."
Digital techniques, which have replaced much of the old photo-chemical processes, have enabled restorers to become more precise in their work and upgrade every single shot in a film such as "Shiraz".
The Indian film is nearly 90 years old but BFI also holds films going as far back as the 1890s.
"Some of them are only a minute long," Dixon said.
"With the 1920s it gets much more complex, because the films get longer and they have a grammar to them which means if you're missing part of the film print, you have to sort of compensate in order to make it understandable for the audience."
Colour and sound add further layers of complexity, although silent films are themselves problematic because they often lack any documents to dictate the speed they should be shown at.
Restoration is a costly endeavour and the archive relies on public funds and private donors, as well as ticket sales from screenings.
"Fiction film, or non-fiction film, is this fantastic record of the whole of the 20th century that people can look at... It is, for those that care to look, a real experience," said Dixon.