Archival documents in this category can include single folios, files and index cards. A file is a collection of documents held together in a folder. The documents within the file are often fastened together using staples, paperclips or pins. The types of documents found on a file can include:

• documents and artworks on paper
• photocopies and laser prints
• thermal papers
• maps and plans
• photographs

Documents can vary in contrast and this may affect the requirements for producing a clear quality digital image. Documents with a well-defined print type with a high level of contrast between the ink and paper and with no discolouration or staining of the paper substrate can be scanned in 8-bit colour. Older documents, with handwritten annotations, poor legibility and low contrast between the text and paper, or where the substrate is faded or stained, should be scanned at a higher bit rate of 16-bit colour.

Files containing multiple documents will be digitised to single page TIFF files, not to a multi-page TIFF.

Any photographic negatives and transparencies attached to, or found within files and documents should also be digitised using the photographic digitisation standards in this document.

1.1   Paper documents under A3

Archival Master - Capture ratio 100% with no manipulation

(Including maps, plans and large format records)

Records larger than A3 cannot fit easily onto a standard flatbed scanner. This may include document types such as maps, charts, architectural and engineering drawings, posters or other large handwritten, typed or printed documents.

Many of these formats contain fine details. Where there is very fine detail, a higher scanning resolution of 600 ppi may be required to produce a more legible image.

Due to their larger dimensions, the scanning of oversize images can produce very large file sizes.

Do not leave oversized records in scanning equipment unattended or unsupported as this can lead to damage.

Oversized materials, including books that have foldouts, must be scanned using equipment that features a scanning bed that is as large, or larger than the item to be scanned.

Do not place glass or other transparent material directly on top of fragile artwork, documents, manuscripts, prints, and photographs with or without mounts. This can cause media to crack or to detach from the item. Use spacers on fragile items to prevent compression between an item and a glass plate.

2.1  Documents over A3 (including maps, plans and large format records)

Archival Master – Capture ratio 100% with no manipulation

2.2 Rare or significant documents, artworks, posters or large format records with a high level of detail

Archival Master – Capture ratio 100% with no manipulation

The term volume refers to an item in the form of a bound book. Volumes may be bound in a variety of styles and materials to protect the pages inside. Types of binding styles found in archival collections may include:

• case bindings where the cover is made separately and wrapped around the text block.
  
  This can include fine, decorative or limited edition volumes, logbooks and diaries
• large leather or suede bound 19th century ledgers and registers
• simple do-it-yourself bindings such as comb or spiral bindings used for business and government reports, diaries and one-off documents
• loose-leaf binders and folders that allow individual leaves to be easily added or exchanged
• post bindings, which use a number of metal posts or screws to hold the binding and the text block together

Handling issues

Flatbed scanners are not recommended for bound volumes. Pressure should not be applied to books in order to flatten them for image capture as this can break the spine or loosen or break off brittle pages in a book.

Books with weak joints or restricted openings should be placed in a book cradle (blocks or rolls of polyethylene foam) during image capture.

Scanning equipment must be adjustable to the height of the collection item to accommodate books that need cradle support.

3.1  Bound Volumes

Archival Master – Capture ratio 100% with no manipulation

Photographic records contain an image formed in a binder layer on paper, resin coated paper, cellulose acetate, cellulose nitrate or polyester base. Black-and-white images are formed by metallic silver particles and colour images by dye layers. In the National Archives’ collection the binder layer most commonly consists of a gelatine emulsion; early processes can also be albumen or collodion. Photographic print images are on a paper (occasionally plastic) base, and negatives or positive transparencies have a clear plastic or sometimes glass base.

Nitrate and acetate-based negatives are prone to deterioration of both the image and base layer. This deterioration can be slowed significantly by storing negatives at low temperature and relative humidity. The only other practical way to preserve the images and make them accessible is to digitise them.

For the purposes of preservation digitisation the photographic collection can be grouped in the categories below:

Prints:

• Colour and black-and-white photographic prints – smaller than A6 (10 x 15cm)
• Colour and black-and-white photographic prints – A6 to A4 (10 x 15cm to 21x30cm)
• Colour and black-and-white photographic prints – over A4 (over 21x30cm)

Transparent materials such as glass can be used to hold the edge of an image flat during digitisation, but care must be taken that the original is not harmed while under pressure. Tightly curled materials must not be forced to lay flat. Care must be taken to assure that flattening a photograph will not result in emulsion cracking, or the base material being damaged.

Negatives and transparencies (including glass plate negatives and positives):

• Colour and black-and-white negatives and transparencies – up to 35mm
• Colour and black-and-white negatives and transparencies – up to 6x6cm
• Colour and black-and-white negatives and transparencies – up to 4”X5"
• Colour and black-and-white negatives and transparencies – over 4”X5” and up to 5”X7”
• Colour and black-and-white negatives and transparencies – over 5”X7” and up to 8”X10”

If using a high-end digital camera, the use of a 5000K light box and calibrated viewing environment is critical when scanning negatives and transparencies. The camera must also capture enough detail to visually resolve the desired ppi. For overhead camera capture fixed focal length, flat field macro lenses must be used. The camera should be capable of capturing at least 14 stops of dynamic range to ensure adequate detail in shadows and highlights.

The initial raw scan of a negative captures all of the information required for a preservation digital surrogate. To make the image accessible, the raw scan is inverted to create a positive image with some adjustments. This may include applying curves to increase or lower contrast and or shadows and highlights for an evenly exposed positive. Image may also be flipped depending on the capture method. For example if capturing emulsion side up using an overhead camera setup the image must be flipped to show the 'right' side. We retain both the raw file and the inverted master file as archival masters.

Film Targets

The use of a film target is essential in determining aim point values for shadows and highlights to ensure no tonal clipping occurs during capture. The film target also allows for correcting white balance and offers optical resolution charts to check for sharpness and focus. Using targets as a reference will provide evidence of consistency and accuracy making it easier to control quality ensuring negatives and prints have been digitised to the same standard.

The RGB/LAB values for the target patches on the digital image should match the values provided from the supplier of that particular target or match values of that target measured from a spectrophotometer, but in general the target should have the following values:

• White – ~240-245 RGB
• Mid Grey – ~110-115 RGB
• Black – ~12-20 RGB

The surrounding space should be around ~250 RGB.

Handling issues

Glass plate negatives may not be put under pressure. They are not always perfectly flat or may have hairline cracks, resulting in breakage when pressure is applied.

Photographic Prints (colour and B&W)

4.1  Colour and black-and-white photographic prints – smaller than A6 (10 x 15cm)

Archival Master – Capture ratio 100% with no manipulation

4.2  Colour and black-and-white photographic prints – A6 to A4 (10 x 15cm to 21x30cm)

Archival Master – Capture ratio 100% with no manipulation

4.3  Colour and black-and-white photographic prints – over A4 (over 21x30cm)

Archival Master – Capture ratio 100% with no manipulation

4.4  Photographic Negatives and Transparencies (colour and black-and-white)

Colour negatives and transparencies – up to 35mm

4.5  Black-and-white negatives and transparencies – up to 35mm

Archival Master – Capture ratio 100% with no manipulation

4.6  Colour negatives and transparencies – up to 6x6cm

Archival Master – Capture ratio 100% with no manipulation

4.7  Black-and-white negatives and transparencies – up to 6x6cm

Archival Master – Capture ratio 100% with no manipulation

4.8  Colour negatives and transparencies – up to 4”X5"

Archival Master – Capture ratio 100% with no manipulation

4.9  Black-and-white negatives and transparencies – up to 4”X5”

Archival Master  – Capture ratio 100% with no manipulation

4.10  Colour negatives and transparencies – over 4”X5” and up to 5”X7”

Archival Master – Capture ratio 100% with no manipulation

4.11  Black-and-white negatives and transparencies – over 4”X5” and up to 5”X7”

Archival Master – Capture ratio 100% with no manipulation

4.12  Colour negatives and transparencies – up to 8”X10”

Archival Master – Capture ratio 100% with no manipulation

4.13  Black-and-white negatives and transparencies – up to 8”X10”

Archival Master  – Capture ratio 100% with no manipulation

Aerial film and photographs form a sub-category of the National Archives' photographic collection. An aerial photograph is a photograph of the ground taken from an elevated position, usually from the air or sky. Aerial photographs provide a straightforward depiction of the physical and cultural landscape of an area at a given point in time. Aerial photographs in particular have fine detail, often require a high degree of enlargement, and may require a higher degree of precision regarding the dimensional accuracy when digitised.

The use of an approved 'film winder' is essential for digitisation activity on wound roll aerial film.

A suitable very high resolution digital camera is used in conjunction with a flashbox light box and a film winder.

For the purposes of preservation digitisation the aerial photographic collection can be grouped in the below categories:

• aerial prints – up to 8"x10"
• aerial prints – over 8"x10"
• aerial film – 70mm, 127mm roll film and medium format roll film
• aerial film – 4 x 5 and up to and including 5 x 7 sheet film
• aerial film – larger than 127mm roll film/ larger than 5 x 7 sheet film
• glass plates

5.1  Aerial Prints – Up to 8”x10”

Archival Master – Capture ratio 100% with no manipulation

5.2  Aerial Prints – Over to 8”x10”

Archival Master – Capture ratio 100% with no manipulation

5.3  Aerial film – 70mm, 127mm roll film and medium format roll film

Archival Master – Capture ratio 100% with no manipulation

5.4  Aerial film – 4 x 5 and up to and including 5 x 7 sheet film

Archival Master – Capture ratio 100% with no manipulation

5.5  Aerial film - Larger than 127mm roll film/ larger than 5 x 7 sheet film

Archival Master – Capture ratio 100% with no manipulation

X-ray film, like B&W photographic film, consists of a silver image formed in a gelatine emulsion on a transparent cellulose nitrate or acetate base. X-rays have the same deterioration characteristics, preservation and storage issues as other film-based photographic materials.

Few scanners are capable of imaging radiographs properly due to their very wide density range and large size. There are specialized film scanners built for this application.

6.1  X-ray Film

Archival Master – Capture ratio 100% with no manipulation

Microform is the term used to cover a range of photographic media employed to copy documents. It includes microfilm, microfiche and aperture cards. A master microfilm is usually black and white silver halide film made from original records. It is used to produce reference copies using less expensive, more robust but less archival dye-based processes on Diazo Film, or a Vesicular Film which produces a positive image (if copied from a negative film) with 10-20 years archival life. Microfilm readers are then used to view or digitise the reference copies.

For the purposes of preservation digitisation the microfilm collection can be grouped in the below categories:

• 16mm and 35mm Microfilm
• Aperture Card – mainly produced with a single frame of 35mm film mounted within the open aperture.
• Microfiche – come in a variety of formats, standard size is 105 mm by 148 mm

Due to photographic limitations of microfilm and the variable quality of older microfilm, it may not be possible to produce what would normally be considered reproduction quality image files. The choice of scanning approach may vary from the recommendations for textual records, and may be more focused on creating digital images with reasonable legibility.

Digital reproductions should be made from a preservation copy of microfilm, if available.

Crop to include the visible edge of pages.

If technical targets are not present on the Microfilm the reduction/scale can be estimated, based on text size and type of document captured. The estimated size/scale of the original document on the Microfilm can then be used to work out the 100% capture resolution.

7.1  Microfilm, Microfiche, Aperture card

Archival Master – Capture ratio 100% of original document size (or best estimate), with no manipulation.

The specifications apply to all physical audio formats including:

• compact cassette
• micro cassette
• mini cassette
• ¼" open reel tape
• gramophone discs
• digital audio tape (DAT)
• CD audio
• 16 mm, 17.5 mm and 35 mm magnetic or optical motion picture film sound.

For audio digitisation the National Archives follows the standards, practices and strategies detailed in the publication: International Association of Sound and Audiovisual Archives (IASA) – Guidelines on the Production and Preservation of Digital Audio Objects (IASA TC-04 Second Edition, 2009). https://www.iasa-web.org/tc04/audio-preservation

The number of audio channels should always be based on the format of the original item, rather than the recorded signal.  For example, a single microphone recorded on a stereo cassette recorder will have a mono signal but the format is stereo so playback and the copy should be stereo.

8.1  Analogue formats (for example Gramophone disc, ¼ inch tape, compact or micro cassette and magnetic or optical motion picture film sound)

8.2  Digital formats (for example DAT)

The specifications apply to all physical video formats containing video, including:

• One Inch, Two Inch
• VHS
• Betamax, Betacam, Betacam SP, Betacam SX, Betacam HD, Digital Betacam
• Video 8
• EIAJ Open Reel, EIAJ Cartridge
• Hi 8
• Umatic
• D2
• Mini DV
• DV Cam, XD Cam, HD Cam
• Laser disc.

For video digitisation the operator must confirm that the aspect ratio is the same as the original, that there is accurate sync between audio and video, and that the preservation file copy displays the same interlacing as the original source tape.

The National Archives is currently reviewing the International Association of Sound and Audiovisual Archives (IASA) – Guidelines for the Preservation of Video Recordings (TC 06) which had its initial release in 2018.

9.1  High definition video

9.2  Standard definition video

Motion picture film held at the National Archives is predominantly on 8mm, 16mm and 35mm gauges. Motion picture film consists of a gelatine emulsion on a plastic support base of cellulose nitrate, cellulose acetate or polyester. The image is formed in the emulsion layer from colour dyes or silver halide particles.

Motion picture film is prone to deterioration due to degradation of the inherently unstable film base. Colour film is also prone to dye fade. Deterioration can be slowed by storing film at low temperature and relative humidity. The National Archives also preserves film through digitisation to industry standard digital file types.

The specifications in this document apply to all physical motion picture film formats including:

• 8mm,  16mm and 35mm  positive and negative film
• Super 8mm, Super 16mm and Super 35mm film.

Motion picture films intended for theatre projection will have been recorded at 24 frames per second, whereas those intended for television will be 25 frames per second. It is important that the film is scanned at the correct frame rate and that magnetic or optical film sound is preserved at its original recorded speed.

10.1  Super 35mm and 35mm positive and negative film

10.2  16mm positive film 24fps

10.3  16mm positive film 25fps (kine, telerecordings)

10.4  16mm negative and Super 16mm negative film

10.5  Super 8mm and Standard 8mm positive and negative film

Access File Format

A derivative file created at the same time or from the Archival Master file. The format is dependent on intended use. As it is not an archival format it can be compressed.

Archival Master File

The Archival Master preserves the essential characteristics of the original records and is uncompressed or has lossless compression.

Audio channel

A single stream of recorded sound with a location in a sound field or a signal that has been stored on media.

AVC High

Advanced Video Coding (H.264 or MPEG-4 Part 10 AVC) is a motion-compensation based video compression standard. As of 2014, it is one of the most commonly used formats for the recording, compression, and distribution of video content.

The standard defines a set of capabilities, which are referred to as profiles, targeting specific classes of applications. This allows a decoder to recognise the requirements to decode that specific stream. The HIGH profile is primary profile for broadcast and disc storage applications.

AVI

Audio-Video Interleave – a file type developed by Microsoft which combines audio and video with varying degrees of resolution and compression.

Bit depth

The number of bits used to represent each pixel in an image or the total number of bits used multiplied by the number of colour channels.

Chroma subsampling

Chroma subsampling is the practice of encoding images by implementing less resolution for chroma information than for luma information, taking advantage of the human visual system's lower acuity for colour differences than for luminance.

Codec

A codec is a software or hardware application that compresses and decompresses data, combining the functions of an encoder and decoder.

Colour space

A geometric representation of colours in space that can be visually perceived or generated using a particular colour model such as RGB or CMYK.

Complete archival record

An archival record is considered complete, when it a whole, legible and accurate representation of the record. This means that all pages, attachments, annotations and enclosures are captured. There is no information missing or obscured through redaction, cropping or any other means.

Compression

Re-encoding data so that it reduces the amount of information required compared to the same data uncompressed. May be lossy or lossless.

Derivative

Derivative files are secondary items produced from the master file. An access file is considered to be a derivative file.

DPX ( SMPTE-268 2003) uncompressed

Digital Picture Exchange (DPX) is a common file format for digital intermediate and visual effects work as defined by the SMPTE standard (268M-2003).

Encoding

A system that modifies a signal prior to recording. Encoding is the process of converting data from one form to another.

Frame rate

Frame rate is expressed in frames per second or fps. It is the rate at which continuous still images (frames) appear on a display.

JPEG

JPEG is a commonly used method of lossy compression for digital images.

MFX OP-1a

Material Exchange Format (MXF) is a container format for professional digital video and audio media defined by a set of SMPTE standards which supports a number of different streams of coded video and audio formats, together with metadata which describes the material contained within the MXF file.

MJPEG2000

Motion JPEG 2000 (MJ2 or MJP2) is a file format for motion sequences of JPEG 2000 images and associated audio, based on the MP4/QuickTime format.

MPEG 4 Base Media / Version 2

MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) under the formal standard ISO/IEC 14496.

MPEG-4 provides a large and rich set of tools for encoding. Subsets of the MPEG-4 tool sets have been provided for use in specific applications. These subsets, called 'Profiles', limit the size of the tool set a decoder is required to implement.

NTSC

Broadcasting system used in North America, Canada and the Middle East.

PAL

Broadcasting system used in Australia, New Zealand and other countries.

PDF

Portable Document Format (PDF) is a file format developed by Adobe, used to present and exchange documents, independent of software, hardware, or operating system. PDF is now an open standard maintained by the International Organization for Standardization.

PDF/A

PDF/A is an ISO-standardised version of the Portable Document Format (PDF). PDF/A differs in that it has been developed for archiving and the long-term preservation of electronic documents. Features present in PDF unsuitable for long-term archiving have been removed.

Raw file

An uncompressed, unprocessed file originating directly from the camera or scanning equipment.

Resolution

This term can describe either how many pixels a monitor can display or how fine a printer can print.

RGB

The RGB colour model is an additive colour model in which red, green and blue light are used to produce a wide range of colours.

Sampling frequency

The frequency (or rate) at which an analogue signal is sampled

TIFF

Tagged Image File Format – is a popular format for storing raster image data and is specified in TIFF Revision 6.0 from Adobe Systems. It has the ability to store image data in a lossless format.

YUV

The YUV model defines a colour space in terms of one luma (Y) and two chrominance (UV) components. The YUV colour model is used in the PAL composite colour video standard. Previous black-and-white systems used only luma (Y′) information. Colour information (U and V) was added separately via a sub-carrier so that a black-and-white receiver would still be able to receive and display a colour picture transmission in the receiver's native black-and-white format.