A Guide to Scanning Motion Picture Film

During my days as a film student, I shot projects using film and digital media. While digital footage was imported directly from tape, film was sent out, developed, and transferred to tape in standard definition. Now that more than a decade has passed and the industry has gone predominantly digital, what options exist for people looking to transfer their existing film? The answer is: film scanning, but how does this differ from the older telecine process? Before undertaking this journey, users will need to be familiar with items such as film scanners, 2K versus 4K, frame rates, output methods, color grading, incurred costs, equipment needed, and more.
Telecine versus film scanning
A telecine is designed to work in real time. The film is played back at normal speed, captured at video or HD resolutions in the proper color space, color-corrected in real time, and written to disk or tape. The speed at which the film is transferred is the native speed of the recipient video format.
Film scanning, on the other hand, is a post process that captures each frame of film to its own file, or to frames of a movie file format such as QuickTime. The result is a significantly higher-quality image compared to telecine, with greater flexibility in post production. The speed at which scanning happens is determined by the speed of the sensor and the resolution, such as 4K at 15 fps or 2K at 30 fps.

Blackmagic Design Cintel Film Scanner

Selecting a lab / film scanner
Choosing where to have your film scanned is an important part of this process, and requires some research. I spent months researching labs and film scanners, eventually settling on a New York-based lab for two reasons: 1) I could drop off and pick up my material personally and, 2) their film scanning was done using a Scanity¡ªa continuous-motion, sprocket-less line imager that uses optical pin registration, a TDI (time delay and integration) sensor, and a spectrally optimized LED light source. HDR scanning is also possible, but this is generally only useful when dealing with high-contrast prints, as opposed to lower-contrast negatives. It is also able to capture audio and more.
Line imagers, area imagers, and pin registration
The Scanity operates by taking a series of narrow images and assembling them into a single frame as the film passes by. This differs from an area imager, such as the Lasergraphics ScanStation, which takes an image of the entire frame at once. Additionally, the Scanity uses optical-pin registration to ensure that each frame is digitally aligned in the sequence using the edges of the sprocket holes as reference points. This differs from mechanical pin registration, where a metal pin holds the film in place, and is a gentler process, especially for older, damaged film.

Sprocketless Optical-Pin Registration

Scanning resolution
Image resolution is all about Ks (2K, 4K), but what does the ¡°K¡± mean? It refers to the number of picture pixels contained in one complete horizontal line of a digital image. A 2K film scan will typically result in 2,048 horizontal pixels per scan line. When a full-aperture Super 35mm film frame (1.33:1) is scanned at 2K, this results in a resolution of 2048 x 1536; while a 3-perf 35mm film frame (1.77:1) produces 2048 x 1157. Both are considered 2K, even though they have different vertical line counts. So, the ¡°K¡± in film scanning refers to the number of ¡°finished picture pixels¡± contained in one horizontal scan line, regardless of the vertical count.

16mm Kodak Vision 250D, scanned at 4K

4-perf Super 35mm Kodak Vision 100T, scanned at 4K

Many argue that 35mm can resolve up to 8K and that anything over 2K for 16mm isn¡¯t needed, while others argue that scanning 16mm at 4K can help with precise detail rendering. I had both my 16mm and 35mm film scanned at 4K. The Scanity used was equipped with a Super 35 Full Aperture gate and a Super16 Full Aperture gate, meaning each gate is optically centered for the middle of the full film image with no academy framing offset. Film is scanned full width, since that is what the sensor is optically set for, with 2K or 4K scans using the full sensor width at that resolution, not the smaller academy film frame aperture. An academy aperture gate would have the sensor calibrated exactly for the academy film frame size and not the full aperture frame.
Since my 35mm material was shot as 4-perf Super 35, a Full Aperture gate was fine, since film shot in a camera with a gate modified as ¡°Super¡± takes advantage of the negative¡¯s full width, including the area usually reserved for the soundtrack. However, for 16mm film, this Full Aperture gate meant that Super 16 framing would be used and sprocket holes would be visible down the right side, making it necessary to perform digital rescaling after the scanning process. In the end, my 35mm material was scanned with a resolution of 4096 x 3112 and 16mm material had a scanned resolution of around 3.6K wide, after being trimmed down from the 4096 x 2480 image size of Super 16.
Bear in mind that 1080p HD scans should be avoided, since they only provide a 16:9 image. If you¡¯ve shot a 4:3 image, it will not capture the entire frame.
Frame rates
The frame rate at which your film is scanned is generally related to how your film was shot and your desired final output, such as DVD, Blu-ray, or a QuickTime movie. All my film was shot at 24 fps, but my initial transfer was done at 30 fps since dailies were delivered on Beta SP. Consequently, sound was also recorded at 30 fps.
I opted to have the scanning done at 23.98 fps and not true 24 fps. I did this because Adobe Encore, which can create Blu-ray media, is not compatible with material shot at 24 fps. While I was concerned that my original 30 fps audio would not sync with 23.98 fps, this turned out to be a moot point, as one second of audio is one second of audio, no matter what the frame rate.
4K versus 2K
I also had 2K scans made, with the goal of finding out if 4K really made a difference. I found that for 16mm and 35mm film, 4K scans were of higher quality than 2K. When comparing a native 2K scan to a 4K file down-res¡¯d to 2K, they looked similar, but 2K files that were up-res¡¯d to 4K did not hold up as well as the native 4K files.

16mm Scanned at 2K

16mm Scanned at 4K

QuickTime versus DPX
Once the scanning process is complete, your film can be output as either DPX files or a QuickTime movie. Very similar to the RAW files used in digital photography, DPX files are uncompressed 10 or 16-bit raw scans that support logarithmic or linear color spaces. One DPX file exists for each frame of film. If you opt for QuickTime files in the linear color space, it¡¯s recommended to get them encoded as 12-bit ProRes 4444.
While DPX files provide the highest quality, they also take up large amounts of storage and require fast disk arrays for playback. My 2,000 feet of 35mm (about 20 minutes) took up 300GB in ProRes 4444 and 1.6TB in DPX. Larger files sizes also lead to increased times for rendering files and copying them to your drive. While color correction, VFX, and compositing software can work with DPX files, NLEs such as Final Cut cannot¡ªat least not without third-party plug-ins.
Color grading
Scans are delivered as ¡°flat,¡± meaning no color correction is applied to the image on capture. The resulting picture is somewhat washed-out looking and requires a second pass in a color-correction system. The advantage of doing a flat scan is that you don’t ¡°bake¡± color-correction decisions, which you may want to change later, into the digital files. This gives you more flexibility in post production.

A graded film scan

An ungraded film scan

So, what are your grading options? Most NLEs have at least basic color-grading tool sets, which can be expanded using third-party plug-ins such as Magic Bullet Suite 12. Blackmagic even offers a free version of its professional color-grading application, DaVinci Resolve, which supports output resolutions up to 3840 x 2160. If you¡¯re not an experienced color corrector, you could hire someone to grade your footage, or just have the material needed for your final cut corrected.
Associated resources
The computer you¡¯ll need to process your film scans depends on the ¡°K¡± of your material. The bitrate for 35mm 4K material was 1.66 Gb/s and 1.3 Gb/s for 16mm, while 35mm 2K bitrates were 425 Mb/s and 340 Mb/s for 16mm, so multi-core systems like the 2013 Mac Pro are well equipped for this type of work. For those who prefer Windows, there is HP’s Z840 Series. When working with 4K material, a dedicated hardware RAID is also recommended, such as the Areca ARC-8050T2. If you want to try your hand at film scanning, B&H also sells the Blackmagic Cintel and the accompanying 16mm and 35mm film gates.
In the end, the decision to have your film scanned, as well as the choices made along the way, is nothing to take lightly. -Additional costs may be incurred for processes such as film cleaning, scanner setup, scanning time, and copying material. You¡¯ll need to provide the lab with a drive on which to copy your material and also need an editing system capable of working with the material. However, a high-res film scan can also help you see your material in a new light, rendering a very natural grain structure with increased detail and dynamic range.