Scottish Screen Archive moving image preservation strategy (PDF)

National Library of Scotland: Scottish Screen Archive
Moving Image Preservation Strategy
A film, video and digital image preservation strategy is best achieved through three
combined methods:
1: Optimum Archival Storage
2: Duplication
3: Digital Data Migration
1. Optimum Archival Storage
From the day of its manufacture celluloid film and videotape will begin to chemically
decay. Images on film will slowly fade and recorded information on videotape will
become corrupt and unplayable. Scientific evidence has shown that temperature and
humidity play a crucial role in the material's lifespan. Placing celluloid film and videotape
in vaults with the optimum storage conditions specified by this scientific research can
slow down the decaying process and extend the lifespan of the film and video by many
hundreds of years. The NLS's main strategy therefore is to preserve the original film
material or videotape for as long as possible in a controlled environment which will
provide the maximum lifespan for the material stored within.
2. Duplication
To be implemented when a film or videotape has been subjected to harsh storage
conditions and has already become badly affected by chemical decay. Priority should be
given to material in this condition, to duplicate the film or video onto new film stock or
videotape thus creating a new archival master. This procedure should be carried out
until film stock or videotape is no longer manufactured. When film and video stock is
obsolete film images should be scanned to 4k, 2k or HD resolution computer files and
these files used for preservation.
3. Digital Data Migration
Film formats have changed little in the last 50 years. Videotape, however, has seen
many changes and various formats have come and gone. Videotape must be transferred
onto another digital video format or loss-less computer file when either, the videotape
shows signs of decay, or the videotape format and playback equipment becomes
obsolete. DVDs and digital image information recorded on future formats must also be
transferred onto the latest computer file before the playback equipment or software
becomes obsolete. This will mean mass migration of the digital information from one
digital tape / file to another. This will be an ongoing process into the future. This digital
data must be securely stored and be recoverable. Multiple backup copies of this data
must be produced and constantly checked and maintained with copies stored on multiple
sites. Migration and data error checking can be set up as an automated process.
Ultimately, in the future all images recorded on film and videotape will end up as
computer files and stored on digital storage devices. This will happen when film and
videotape has ceased production and moving images and sound information, both
professional and amateur, are all recorded on the latest digital storage devices.
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A. Motion picture film preservation
All gauges of film stock are preserved by Scottish Screen Archive, these include:
35mm, 16mm, 9.5mm, 8mm standard, Super 8mm plus other rarer gauges if required
There are two routes for preserving celluloid stock:
1: Storage in controlled environment
2: Duplication of deteriorating originals to modern film stock
These are not mutually exclusive. The size of Scottish Screen Archive's divisional film
collection requiring to be duplicated for preservation vastly exceeds the capacity of the
Scottish Screen Archive's financial and technical resources. The principal strategy
therefore is to preserve the film material through storage in a controlled environment,
thereby stabilising the collection against further deterioration, and buying time for any
duplication in the future. The small annual divisional budget for preservation duplication
will be reserved for those specific classes of material under threat from chemical decay
and for which long term storage is not an appropriate conservation strategy.
1. Preservation through storage
Storage conditions are vital in preserving celluloid motion picture materials. Cold
temperatures and low relative humidity will increase the lifespan of film stock by
hundreds of years. This will prevent the fading of colour dyes and fungus growth.
Materials affected by acetic degradation, known as ‘vinegar syndrome,’ require to be
stored at sub-zero temperatures to slow down this autocatalytic chemical reaction. The
time taken for motion pictures to degrade to destruction depends on three main factors,
stock type, storage conditions and processing quality. Nitrate and acetate film stock can
become chemically unstable within a short period of time if stored at high temperatures
and humidity. Badly processed film also speeds up chemical decay. The main NLS
preservation strategy should be to aim for optimum archival storage conditions in its film
vaults.
Film Type
Colour and Nitrate Film
Black and White Film
Film with Commag Soundtrack
Magnetic Soundtracks
Optimum Archival Storage Conditions
-20 degrees centigrade / 30% relative humidity
-10 degrees centigrade / 30% relative humidity
10 degrees centigrade / 35% relative humidity
10 degrees centigrade / 35% relative humidity
New scientific research may mean that optimum storage conditions may change in the
future. NLS should be prepared to modify storage conditions based on any new
scientific evidence or experience gained.
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2. Preservation through duplication
The following classes of film will be prioritised for duplication:
Nitrate film stock: Due to the inevitable chemical breakdown, the hazardous
nature of nitro-cellulose stock and the fact that NLS cannot
store large quantities of material on site for safety reasons.
Acetate picture or magnetic soundtrack affected by vinegar syndrome.
Magnetic soundtracks must be rerecorded onto new magnetic stock or digitised.
3. Digital technology
Digital technology will eventually take over from motion picture film. s this technology
increases its hold on moving image production and exhibition, traditional photochemical
film laboratory services will decline and film duplication stocks will be phased out.
Eventually motion picture film stock manufacture will cease to exist. 35mm film should
be scanned at a resolution of at least 4k and 16mm film at 2k. Digital technology will
eventually become a major ally in film preservation, enabling the duplication of the
celluloid image and sound information onto digital formats without any loss of picture or
sound information.
B. Videotape preservation
The Scottish Screen Archive preserves a range of videotape formats including:
1 inch, Sony 1/2 inch, U-Matic, Hi-8, VHS, S-VHS, Betacam SP, Digital Betacam, Mini DV,
HDCAM, HDCAM-SR and others
1. Preservation through storage
Videotape masters should be stored in a cool and dry environment. This will greatly
increase the original tapes’ lifespan. Videotape kept outwith proper storage will degrade
over time. Videotape can become chemically unstable within a short period of time if
stored at high temperatures and humidity. Lubricants used in the original tape formula
will start to separate and extrude onto the tape surface. This will cause the tape to stick
on the video player drum and make it impossible to play back the recording.
The main NLS preservation strategy should be to aim for optimum archival storage
conditions for its video and magnetic recordings.
Videotape Conditions
All formats
Optimum Archival Storage Conditions
10 degrees centigrade / 35% relative humidity
Preservation through duplication
Videotape formats are in a constant cycle of change, driven largely by the market
interests of the manufacturers of the hardware. Any preservation strategy for archival
materials must be prepared to embrace a culture of format migration as the commercial
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market develops and new formats become the industry standard. The only variable is
when, not if, collections require to be transferred.
The preservation of magnetic tape is best served by the monitoring of its condition and
transfer onto a new format before physical degradation renders it unplayable, or the
format becomes obsolete.
Due to the complex technical design of video equipment, once the recording equipment
becomes obsolete and parts become difficult to obtain, the transfer of large amounts of
tape will become very difficult if not impossible. When new digital formats appear, there
is a period of a few years before a decision can be made with regards to which format
the archive chooses for its master.
NLS should aim to transfer all obsolete video formats onto the current broadcast format,
which is currently Digital Betacam. This should be carried out as a matter of urgency.
When digital computer storage becomes cheaper and more reliable images recorded on
videotape should be transferred to computer files using a loss-less and error checking
transfer process.
Priorities for duplication will be:
Obsolete formats - collections on formats not currently commercially available:
1” C format, Sony 1/2” open reel, Betamax, U-Matic
C. Future digital formats and movie files
Digital Cinema Packages (DCPs), digital files, digital videotape formats, DVDs, Blu-ray
discs, digital memory cards and future digital formats.
When film and videotape has ceased production moving images and sound information
both professional and amateur will all be recorded on digital storage devices.
The strategy for current and future digital formats must be to migrate the digital
information whenever the digital format or playback software becomes obsolete. This
process must be loss-less with no digital compression or errors. Error checking systems
or software must be in place to make sure that all the data has been transferred
completely and correctly. This digital data must be securely stored and be recoverable.
Multiple back-ups must be stored on multiple sites. In the future all images recorded on
film and videotape will be transferred onto computer files and stored on digital storage
devices.
Alan Russell
Technical and Preservation Manager
Scottish Screen Archive, NLS
May 2013
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