DFT Protects Precious Film Assets by Scanning
While looking around IBC 2024, we spotted a poster that showed the film Mahabharata which had been scanned in 8K to create an archive. We spoke to the company that was showcasing the machine that had been used to perform the scanning. That company was Digital Film Technology GmbH (known as DFT) which has, in different corporate forms, a long history in scanning of film – over 75 years.
We followed up to learn more about the company and its interest in high resolution scanning and interviewed Simon Carter, the firm’s EMEA and APAC Sales Director. It’s owners had included Philips, Thomson and Grass Valley, but around 2012, there was a rapid and dramatic drop in the production of commercials on film. Feature film production has slowly, and still not completely, transitioned to using digital capture, but the world of commercials changed rapidly.
DFT was only one of the firms that had to change course around that time. Cintel, a company founded by TV pioneer John Logie Baird, also got into difficulties and was acquired by Blackmagic Design. In 2012, DFT was acquired by Prasad Corp and changed its emphasis.
Although feature film scanning has continued, with the change from film to digital in post-processing, DFT has moved its focus to the use of scanning to create digital archives from film. As a result, it has clients all around the world as ‘Every country has a film institute’, many of them FIAF members. In the last year, DFT has supplied scanners to the Polish National Film Archive, the Malaysian Film Archive and Germany’s National Film Archive, Bundesarchiv.
Film Assets Can be Precious and Fragile
These digital assets not only have to be of the highest quality, they are often very fragile, Carter highlighted. It is not uncommon for the company to only have one chance to run the scanning process. Film can be decayed and shrunk and it is often not of any commercial value, but of high social or historical value.
The Scanners
The concept of the Scanity range of film scanners from DFT is line scanning, with a continuing feed of the film. The content can be processed in real time, but the limit of resolution using this concept is 4.3K.
Over time, there has been a demand for even higher resolution. As Carter explained, it can be a tricky question to decide what resolution to scan at. While film grain is often high resolution (see our recent article on this topic), the content itself may not be. To achieve a true resolution of 4K or more on film, the content needs to have been well created and shot with high quality prime lenses. You also need to have an original negative for scanning rather than a copy. Carter told us that the true resolution limit for 35mm film, as far as DFT is concerned, is in the range of 8K.
If you scan at the 4K/6K range, you can run into aliasing issues of high frequency content (it’s that Nyquist thing again – ed.) so there is a new interest in mastering at 8K. This gives a lot of latitude in subsequent processing and Carter told us that the 8K content can be more efficiently compressed compared to 4K (he referred to a paper by Peter Swinson, a specialist in the telecine area). As we have written, the use of 8K to scan more accurately captures grain from film content better.
Matching Human Vision
Carter has an interesting idea about why humans are quite comfortable in accepting cinematic content that is presented in what should be very artificial ways. He sees the kind of image that is presented in relatively low resolution and in black and white as similar to the way the human visual system works in low light (scotopic vision – ed.) and that helps the ‘suspension of disbelief’.
For the 8K scanner that we saw at IBC, the Polar HQ, has a 9.3K area imager. The imager is monochrome and can scan more than the image area of the film, capturing the border and perforations ( edge to edge) including audio information. It can overscan by up to 25% and supports 4K, Super4K and 8K output deliverables . It uses RGB LEDs to flash the image as it is held stationary under the sensor. As we saw at IBC, the scanner uses variable loops either side of the imager to keep the film under constant tension while the frame that is being scanned is static. That helps to minimize the chance of damage.
Compression is Avoided
DFT tends to hand off data in a very unprocessed format as many of the archival projects try to avoid compression. Data is usually supplied in 10 bit log or 16 bit linear formats and using DPX files.
A downside of not processing the content is that you tend to get the image ‘warts and all’ and that can include dust and scratches. One option to handle this is to use an extra alpha channel in the image content to store an infrared scan of the image, allowing the detection of dust and other issues. Infrared scanning shows up the damage much better than visible light, but can only be used on color film.
Correcting the Challenges of Film
Automated correction can be used, but the algorithms need to be optimized for different sizes of defects and automation is not ideal for archiving. AI processes are improving this, but run the risk of adding bad information. On the other hand, manual correction is very laborious, and while it might make sense for commercial content, is unlikely to be viable for archives.
DFT offers the option of ‘wet gate’ scanning. In this process, Carter explained, the film is fully immersed in tetrachloroethylene, also known as perchloroethylene (or Perc). The scanners have an ‘aquarium’ style bath system that minimizes bubbles and using this process typically eliminates 60% to 70% of the surface issues and has the advantage of cleaning the film. It works on black and white as well as color film.
However, wet gating increases the cost of the scanners and the Perc (which is used because it has the same refractive index as the film) is a hazardous substance whose use is being discouraged for environmental reasons. As a result, the technique tends only to be used by organizations that previously have the processes and procedures in place to deal with the substance already. Simon Carter told us that in Hollywood, the sale of such equipment is banned unless studios or facilities already have licenses to use Perc.
Mahabharata Was a Big Project
Returning to the Mahabharata project that first drew our attention to DFT, there is an intriguing article in Variety that explains that “there were 3,451 reels of negative and sound elements scattered across various laboratories were collated”.
The 8K scan was stored with a 16-bit depth format and that created 450 Terabytes of data. The resulting version of the film is transformative, according to Simon Brook, the son of the original director, Peter Brook.
“It’s not in the sharpness, it’s very much in the color depth,” he explains in the article. “It’s as if there’s a kind of luminosity, a glowing life-like feeling that comes out that almost makes the brain think it’s in 3D. It’s very strange.”
