Tuesday, July 19, 2005

Restoring Movie Images Digitally

It's probably no secret that this blogger thinks of movies as reason number one to climb on the HDTV bandwagon. To look their best in hi-def form, classic films, middle-aged films, and even fairly recent ones often need restoration work. In Robert A. Harris, Film Restorer Extraordinaire I discussed the work of one of film restoration's leading lights, a man whose contributions (usually along with partner James Katz) include preserved versions of Vertigo, My Fair Lady, Spartacus, Lawrence of Arabia, and Rear Window.

Now I'd like to take a look at the contributions to film restoration that are arriving from an entirely different quarter: John Lowry's Lowry Digital Images.

LDI has been responsible for returning the first three Star Wars films "to their original glory for DVD," says "Creating the Video Future," an article in the November 2004 edition of Sound & Vision. Ditto, the Indiana Jones collection. Ditto, all twenty of the James Bond films. Ditto, Snow White and the Seven Dwarfs; Singin' in the Rain; North by Northwest; Gone with the Wind; Now, Voyager; Mildred Pierce; Roman Holiday; Sunset Boulevard; and Citizen Kane.

The Lowry process is not unlike that used for digital intermediate work (see
The Case of the Data-Processing DP). The first step is to scan into the digital domain each frame of the film negative, often at 4K resolution (see 2K, 4K, Who Do We Appreciate?). At four seconds per frame, I calculate it must take 691,200 seconds, or 192 hours, to scan in a two-hour film at 4K. That's a ratio of 96 scan hours per one running hour, excluding coffee breaks!

Lowry stores the entire film as data on servers that hold 6 terabytes
apiece. A terabyte is 2 to the 40th power, or 1,099,511,627,776 bytes. Think of it as 1,000 gigabytes. Lowry has a total of 378 terabytes of storage hooked to his high-speed network. Perhaps the Pentagon would like to send a task force to check out how it all works.

That data network at LDI also interconnects 600 dual-processor Macintosh computers whose task it is to process all that stored data, using complex algorithms selected and parameterized according to the needs of the particular movie, in order to tweak the look of each of the 172,800 frames that make up a two-hour flick.

After a visual review of each scene on a video monitor and a possible re-parameterization and rerun of the automatic process, exceptionally problematic material is touched up "by hand."

When all that is done, the result is a "digital negative." The digital negative is said by Sound & Vision's Josef Krebs to be "every bit as good as the camera negative — but without the wear, tear, and deterioration." The digital negative can be used to spin off versions for DVD, HDTV, standard-def TV, or digital cinema, a filmless methodology which involves using digital video projectors to throw the image onto the screen in commercial theaters. Or it can be output on film for optical projection.

Darth Vader in Star Wars
For the story on how this process gave the original Star Wars films new life, check out "John Lowry: Three Months and 600 Macs" on the Apple Computer website. Job One was to obliterate dirt and scratches, Lowry says. The next challenge was to conceal the telltale changes in contrast, graininess, and definition that accompanied the optical special-effects scenes in those pre-CGI days. Lowry says he also "sharpened it end-to-end, reduced the granularity and got rid of the flicker."

"When you use a computer," says Lowry, "if you can understand the problem, it's always solvable." Torn film, fading, chemical deterioration — they all succumb to digital remedies.

4K-resolution scanning is not always used as the basis for his digital restorations, Lowry says ... after having extolled 4K as uniquely giving the ability "t
o capture everything that is on that negative, which probably has a limit somewhere in the 3- to 4K range."

The "information on a film," he says, "
usually rolls off between 3 and 4K. We've experimented at 6K, but, frankly, it's pointless on a standard 35mm film frame until there are better camera lenses and film stocks." So, 4K looks like a winner when it comes to really, really capturing the whole image present on the original camera negative. Also, Lowry says, "with 4K the colors are more vibrant, subtle, and sharper."

Even so, Lowry did standard-def (!) transfers for
North by Northwest; Now, Voyager; and Citizen Kane. Snow White and the Seven Dwarfs and Giant were his first digital restorations at high definition (1080p, I assume). Next came the step up to 2K, for Roman Holiday and Sunset Boulevard; they had to be scanned from duplicates of their original negatives, with accordingly lower resolution to begin with, to be captured digitally.

Lowry's current maximum resolution, 4K, is newer yet. "
Now we do most of our transfers at high-def and 2K," he says, "but we also do a whole range of movies in 4K." I'll bet the demand for 4K will, despite the extra cost, soon outstrip that for 2K and HD. I'll furthermore bet that there's already little remaining demand for SD restorations.

Along those lines, Lowry says that he is doing nine of the twenty James Bonds in 4K, the rest in HD. I'll wager the day will come soon in which the film's owners wish they'd scanned them all in 4K.

Film preservationist Robert Harris, in his
"Yellow Layer Failure, Vinegar Syndrome and Miscellaneous Musings" column at TheDigitalBits.com, has sometimes been critical of the Lowry process. One reason is that Harris describes himself as a "proponent" of film grain. "Grain is our friend," he has written. The Lowry process can remove most or all of the grain in a film image. Not just the excessive grain which builds up whenever film is duplicated from camera negative to interpositive to internegative ("dupe" negative) to final print — all the grain, period.

Lowry's S&V response: "We generally try to even out the grain so changes don't interfere with the storytelling. I don't recommend taking all the grain out of anything. I used to do more of that. We took out too much grain on Citizen Kane, but on Casablanca we left more in and it looks better. There's something comforting about grain for the viewer." It sounds like Lowry has become a late convert to the grain-is-our-friend school of film preservation.

Another complaint Robert Harris has made is that the Lowry process doesn't really restore or preserve the film per se. It leaves the photographic images which were originally recorded on celluloid strictly alone. It does not yield a replicated negative or fine-grain positive separation masters for archival use. It does not result in any film elements whatever, other than (optionally) a new generation of release prints derived from the "digital negative."

But release prints are not archival. They're the end of the line, photo-optically speaking. You can't use them as sources for further duping, since they lack the negative's high level of detail, low level of grain, wide dynamic range/contrast ratio, and so forth. And, due to "blocking," the shadows and highlights in a final print are drained of nuance.

So the Lowry process places the entire burden for archiving film's images squarely in the digital-video domain. The film isn't preserved for posterity; at best, the data is.

Though I don't know that I can put my finger on the source — I believe it to have been an interview I read with prime digital-cinema mover George Lucas — I've read that Lowry's precious data eventually is remanded to the studio to whom the film belongs. Or else the studio provides Lowry with the (empty) storage media in the first place, and then receives the (filled) media back at the end of the process. Something like that.

That means the studio winds up in charge of archiving the data. In the past, studios have been (shall we say) notably remiss in taking proper care of their archives.

What's more, data-file formats are notorious for their quick obsolescence. The file formats used for digital intermediates have yet to be standardized, and I'm sure those Lowry uses for "digital negatives" are just as idiosyncratic. In twenty years, will machines still be able to read these files? That's Robert Harris' main concern, I gather.

Still, the process John Lowry uses to restore not film per se but film's images is an impressive one. It's clearly the wave of the future. Hollywood is already beating a path to his door.

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