Motion picture film scanner
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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 or 4K film resolutions. (2K is approximately 2048×1536 pixels and 4K is approximately 4096×3072 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 colour 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.
The scanned footage is edited and composited on work stations then mastered back on film, see film out and digital intermediate. Scanned film frames may also be used in digital film restoration. The film may also be projected directly on a digital projector in the theater. The film may be converted to SDTV (NTSC or PAL) video TV systems.
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[edit] Imaging device
- The front end of a motion picture film scanner is similar to a telecine. The imaging system may be either a charge-coupled device (CCD), a complementary metal–oxide–semiconductor (CMOS) or cathode ray tube (CRT) imaging pick up.
- A lamp is used as the light source in a CCD imaging front end. The CCDs convert the light to the video signals.
- In a CRT imaging system the CRT (also called a Flying spot tube) is used as the light source and part of the scanning system. Photomultipliers or avalanche photodiodes are used to convert the light to electrical video signals.
- A prism and/or dichroic mirrors or colour filters are used to separate the light into the three: red, green and blue, imaging pick up devices.
[edit] Image processing
- The three color signals are electronically processed and color graded. A 3D look up table (3D LUT) is usually applied to the RGB values before it is coded into the DPX output files.
- The DPX files are usually outputted though a network port cable or an optical fiber port: HIPPI, fiber channel or newer systems like gigabit Ethernet. A computer then stores the files on to hard drives of a storage area network for later processing and use.
[edit] Models
- Single frame intermittent pull-down (about 1 fps):
- Kodak's Cineon, the first system designed for DI work, included a scanner, tapes drives, workstations and a film recorder.
- Lasergraphics - The Director 9 fps (HD, 1.85 and 3-perf); 6.8 fps (2K full aperture); 1 fps (4K full aperture); 8 fps (16mm HD or 2K)
- ARRI scanner, Arriscan
- Filmlight - Northlight Film scanning, single frame intermittent scanner
- IMAGICA Technologies Corp. - IMAGER XE single frame intermittent scanner
- Cintel's diTTo
- Continuous motion scanning:
- Spirit DataCine - SDC2000 with data option, DFT Digital Film Technology (2K realtime at 24 fps or 4K scans at 6 fps) (can be switched to telecine mode)
- Spirit DataCine 4K/2K with the data option, DFT Digital Film Technology (2K realtime at 24 fps or 4K scans at 6 fps) (can be switched to telecine mode, only if it has this option)
- Cintel's C-Reality/DSX and ITK - Millennium/dataMill.
- Image Systems GoldenEye 2K at 12 fps, 4K at 6fps
