How Motion Picture Film Is Duplicated and Distributed

Having developed the enormous negatives out of my Mamiya RZ67, I couldn’t help but wonder what would happen if I photographed them on another colour negative. Would the image become a positive?

As I proceeded with this explorative exercise, my research led me to learn about an essential component in the motion picture finishing process that I had inadvertently approximated: interpositive film.

Interpositive film was vital in cinema production before digital editing workflows became the norm. Back then, getting movie reels finished and delivered to the theatres involved many steps.

Modern movies* that are shot on film go through the digital intermediate workflow, which makes production much cheaper while suffering less quality loss from analogue distortions. And so is the case with still photography, where most of our images are scanned, colour-corrected using software, and distributed on websites/via e-mail/on social media.

✱ — Except for Cristopher Nolan’s movies. His features are still shot and distributed via purely analogue workflow parallel to the digital release.

In this article, I’ll contrast the traditional process of film finishing and duplication to modern workflows and review a few contemporary examples of movies that used either. I’ll also discuss how the interaction of digital processes and the analogue medium have given film (whether still or cinema) a new life in the modern world.

How movies were edited and distributed in the pre-digital era.

Before we could use computers to edit video footage, film had to go through multiple duplication steps. The cutting and stitching had to be done by hand or on a special machine that would aid the mechanical process. Each time it got duplicated, there would be some degradation in resolution and colour quality. But to make a good movie, it would have to happen a few times:

Having shot all the takes, the film camera reels would be developed as negatives and cut into a cohesive sequence called a work print. This was aided by transferring the film onto videotape and using the result to composite the images as positives, which then got “locked” and programmed into another machine that would automatically cut the camera negatives. Before the 1960s, this work was done by hand with some mechanical assistance.

The re-assembled camera film would then get duplicated via wet gate: a process of contact printing while submerged in liquid (which improves the transfer quality). This technology is obviously superior to my experimental half-frame capture of the medium format negative (above). But the idea is similar: capturing a film negative on a second film negative to create a positive image, called interpositive film.

Interpositive film is used for layering colour corrections, special effects, transitions, and dubbing. Once the first pass of the work on interpositive is done, a new transfer is made into an answer print (also a positive) — a rough assembled copy used for approval or planning further changes, which would then be reflected on consequent answer prints.

Once the final answer print is approved, interpositive film is transferred onto a new negative, called internegative. Internegative is then used to create numerous transfers onto release prints, which are the copies that movie theatres get.

At this point, the film that goes into the theatre projector is a third-generation copy (camera film › interpositive › internegative › release print). Even with the best image transfer technology in the world, some loss of quality is unavoidable.

You may wonder why the studios would bother transferring their interpositives to an internegative and then the release copies. So did I; for this article, I’ve learned that those steps were necessary to 1) protect the interpositive film from wear and 2) maintain the contrast and colour accuracy.

Interpositive film is the most important copy the studio can have in its possession. It is the final version of the movie, often dubbed “Protection IP,” i.e., to be protected. But, due to the mechanical nature of film transfers, they create wear, so it would be inadvisable to run IP through a wet gate repeatedly, degrading and potentially endangering the production. Internegative film takes the brunt of that abuse instead of the IP; in some cases, internegatives had to be re-made from interpositives because of the wear, but that didn’t have to happen many times.

Additionally, positive (reversal) film is not used for transfers because contact printing from positive to positive causes contrast and saturation to increase significantly, ruining the picture. Negative film’s linear curve, on the other hand, preserves image quality.

How movies (that are shot on film) are distributed in the digital era.

Though digital cameras dominate movie sets today, many are still shot on film. Some examples are Blade Runner 2049, Once Upon a Time… In Hollywood, and La La Land. However, those films almost certainly use a process that differs from the one described above:

Digital intermediate workflow in movie production is simpler, less prone to quality loss*, faster, cheaper, and a lot more powerful when it comes to visual effects. The process usually involves just one set of film reels — the one in the camera(s). Instead of multiple image transfer steps, film is scanned, and the media is worked on in the digital environment, then distributed digitally. In some cases, the digitally-edited copy of the film may be used to expose release prints using specialized digital projectors.

Some films that are shot and edited digitally go through the “analogue intermediate” process, which involves exposing reels of film to the digital images and then scanning that film. This is done to add the unique character and the look of an emulsion.

✱ — The amount of quality loss during contact printing vs. scan & digital intermediate print may be debatable, and the types of quality loss depend greatly on the scanner and the film stocks.

Cristopher Nolan’s IMAX film duplication and distribution.

Cristopher Nolan is adamant about using an uninterrupted analogue workflow for his movies. Oppenheimer is not an exception. Shot on Kodak film, including the special version of Kodak XX black and white stock, it went through all the steps of contact printing: camera › interpositive › internegative › release prints.

But of course, there are significant differences between Oppenheimer and films shot in the 1960s — both in the quality and the workflow. In addition to the enormous IMAX negatives, modern Kodak emulsions have much tighter grain and significantly better colour management than the decades-old technology. And instead of the tape transfer step, the camera film was scanned and edited digitally; those edits were then programmed into a machine that applied them to the film.

If you’re lucky enough to have seen Oppenheimer in a theatre with a film projector (whether IMAX or 35mm), you’ve experienced a movie that was never digitized. But for most of us, it’s been scanned and viewed on a screen, much like the film photography on this website.

Source: Jay Trautman, who worked as an Assistant Editor for Oppenheimer, explained the process on YouTube; the video has been since taken down, but a copy remains on Internet Archive.

Digital intermediation is the easiest way to interact with film — whether it’s a movie, a TV show, or still photography. It has some downsides; as many film photographers will tell you, high-quality scans are difficult to make. There may be some loss to the dynamic range, and dealing with colour is another challenge.

But there are undoubtedly advantages to digitizing film also. Aside from being able to distribute as quickly as digital images (and giving it a fighting chance in the modern world), well-scanned film stands out from digital photographs. Many people like that, and the ability to replicate the film look faithfully is debatable.

The relative affordability of still photography compared to motion pictures, the unique visual qualities of film, the ease of digital editing/distribution, and the process have given a massive bump to the medium’s popularity in recent years. Better yet, we can “play Cristopher Nolan” by printing our negatives directly on paper — at home or in a community darkroom.