Digital Intermediate Primer

Back in the “golden era” of film production, perhaps thousands of feet of 35mm negative (the same stuff you put in a non-digital stills camera) were generated every day of a shoot. All this film would have to be soaked in numerous chemical baths, and then it would all get printed onto more film, this time 35mm “positive” (or “reversal”) film. This allowed a light to be shone through, projecting the image onto something (like a cinema screen) in the correct colour, for viewing.

So, at the end of shooting a production, you’d have maybe a million feet of celluloid, at which point would come the editors to sort through it all, which had to be done by hand. But because the negative is so fragile and yet so valuable (each bit of original negative retains the highest level of quality, and represents all the set design, acting, camerawork and lighting invested in it), there was constantly a risk of damage to it particularly during editing, but also during duplication and printing.

More copies of the negative were created for the editors to work with, and once they had decided how it was going to cut together, they’d dig out the original and match all the cuts and joins they made (and they really used scissors and glue to do it) to the original.

So now there would be a cut together film, which consists of hundreds of valuable strips of film, held together by little more than tape. Woe betide any filmmaker who decided they wanted to make changes to it now.
But there were other problems to deal with. First of all, you don’t want to keep running a priceless reel of film through a duplicator every time you want to make a cinema print (especially bearing in mind that they might need to make some 10,000 or more prints for a typical distribution run). Secondly, different scenes might have been shot on different days, so the colour would need to be adjusted (or “timed”) so that they match better.
Hence the internegative and interpositive copies of the original, cut-together film. Creating these additional reels allows for colour-timing to be done too, and so the result is a single piece of film with no joins, and so now everyone’s happy, even after running it through the copying machine 10,000 times.

Well, almost. See, the internegative is of significantly lower quality than the original, and all the colour-timing is done using a combination of beams of light, coloured filters, and chemicals, which is equivalent to trying to copy a Rembrandt using finger-paints. But, until the digital intermediate process gained a degree of authority, filmmakers (and the audience) just lived with it.

The digital intermediate (or “DI” for those guys who are obssessed with acronyms), as it relates to film production, was first developed to replace the photographic internegative. Very simply, you take all the negative that’s been shot (people still shoot films on film, and probably will for many years yet), and put it on a datacine or a scanner- a machine that eats film and spits out pixels (very much like a telecine- which instead spits out video). All the data is then assembled together in a non-linear editing type system (rather than scissors and glue), and all manner of effects, titles, and colour-grading is possible. You can even repair damage to the original negative, like if there are bits of dust on it (which seems to be an amazingly frequent occurence). And every copy is perfect. And to satisfy the diehards (and the cinemas), this can be regurgitated back onto 10,000 film prints, using a combination of digital film recorders and photochemical duplicators.

So that’s how it relates to film, but can the digital intermediate paradigm be applied to other media? Absolutely. In a sense, the original medium becomes somewhat irrelevant when working digitally. Video productions have long ago abandoned tape-to-tape (or “linear”) post-production in favour of digital ones. This gave rise to a multitude of possibilities such as the artistic colour palette of many music promo videos, to the high degree of control for editing feature-length documentaries. And of course, using a digital pipeline means you can still output to any number of formats, even 35mm film for cinema projection.

So what is a Digital Intermediate?
At the moment, precise definitions vary, or are subject to strong argument. I would suggest the following definition:
a “digital intermediate” is the process of creating motion picture content using digital means, regardless of the source or destination material.

Jack James has been working with digital imaging technology for 10 years. He has worked within a number of digital intermediate environments since joining Cinesite (Europe) Ltd.’s Digital Lab in 2001 to work on HBO’s Band of Brothers.  He has a number of film credits, and has published the book "Digital Intermediates for Film & Video" with Focal Press.

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Posted: March 8th, 2005