Motion picture film scanner

A motion picture film scanner is a device used in digital filmmaking to scan original film for storage as high-resolution digital intermediate files.

A film scanner scans original film stock: negative or positive print or reversal/IP. Units may scan gauges from 8 mm to 70 mm (8 mm, Super 8, 9.5 mm, 16 mm, Super 16, 35 mm, Super 35, 65 mm and 70 mm) with very high resolution scanning of 2K, 4K, 8K Video Format, or 16K resolutions. (2K is approximately 2048×1080 pixels and 4K is approximately 4096×2160 pixels).

Some makes of film scanner are intermittent pull-down film scanners which scan each frame individually, locked down in a pin-registered film gate, taking roughly a second per frame. Continuous-scan film scanners, where the film frames are scanned as the film is continuously moved past the imaging pick up device, are typically evolved from earlier telecine mechanisms, and can act as such at lower resolutions.

The scanner scans the film frames into a file sequence (using high-end data storage devices), whose single file contains a digital scan of each still frame; the preferred image file format used as output are usually Cineon, DPX or TIFF, because they can store color information as raw data, preserving the optical characteristics of the film stock. These systems take a lot of storage area network (SAN) disk space. The files can be played back one after each other on high-end workstation non-linear editing system (NLE) or a virtual telecine systems. The playback is at the normal rate of 24 frames per second (or original projection frame rate of: 25, 30 or other speeds). Each year hard disks get larger and are able to hold more hours of movies on SAN systems. The challenge is to archive this massive amount of data on to data storage devices.

Film scanner

A film scanner is a device made for scanning photographic film directly into a computer without the use of any intermediate printmaking. It provides several benefits over using a flatbed scanner to scan in a print of any size: the photographer has direct control over cropping and aspect ratio from the original, unmolested image on film; and many film scanners have special software or hardware that removes scratches and film grain and improves color reproduction from film.

Film scanners can accept either strips of 35 mm or 120 film, or individual slides. Low-end scanners typically only take 35mm film strips, while medium- and high-end film scanners often have interchangeable film loaders. This allows the one scanning platform to be used for different sizes and packaging. For example, some allow microscope slides to be loaded for scanning, while mechanised slide loaders allow many individual slides to be batch scanned unattended.

Dust and scratches

Dust and scratches on the film can be a big problem for scanning. Because of their reduced size (compared to prints) the scanners are capable of resolutions much higher than a regular flatbed scanner; typically at least 2000 samples per inch (spi), up to 4000 spi or more. At these resolutions dust and scratches take on gigantic proportions. Even small specks of dust, invisible to the naked eye, can obscure a cluster of several pixels. For this reason, techniques have been developed to remove their appearance from a scan, see film restoration.

Film stock

Film stock is an analog medium that is used for recording motion pictures or animations. It is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast and resolution of the film.

The emulsion will gradually darken if left exposed to light, but the process is too slow and incomplete to be of any practical use. Instead, a very short exposure to the image formed by a camera lens is used to produce only a very slight chemical change, proportional to the amount of light absorbed by each crystal. This creates an invisible latent image in the emulsion, which can be chemically developed into a visible photograph. In addition to visible light, all films are sensitive to X-rays and high-energy particles. Most are at least slightly sensitive to invisible ultraviolet (UV) light. Some special-purpose films are sensitive into the infrared (IR) region of the spectrum.