# /programs/ourwork/past/culturalmaterials/surrogates.htm

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# Preparing Digital Surrogates for RLG Cultural Materials Recommendations for digitizing Recommended background Digital conversion service bureaus Suggestions for exisiting surrogates ## Recommendations for digitizing Images Textual materials Pictorial materials Audio Motion Complex digital objects File naming Submission These are general recommendations, not absolute requirements. Since each digitization project is unique, there may be very good reasons for using alternative quality guidelines or for choosing a different approach (although we strongly recommend that you be consistent within a project). For RLG-funded digitization, please discuss intended variations from these recommendations with Ricky.Erway@oclc.org. For other projects, consider this guidance in the context of your organizational requirements and proceed accordingly. ### Images Avoid device-specific color space, format, headers, etc. Size and save page images at 1:1 scale to the dimensions of the original pages. For optimal sharpness, view images on the monitor at 100 percent (i.e., each pixel on the screen representing each captured pixel of the image). Evaluate an area of the image that depicts details and edges. Be sure the whole image area (with edges) has been scanned and no part of it has been cropped. Scan the image in the correct orientation or correct the image orientation in postprocessing. Avoid skew by placing the originals squarely on the scanner. Rescan a skewed image rather than rotating it after scanning. Check for artifacts such as dropout lines or pixels, banding, lack of uniformity, poor color registration, aliasing, flaring, and contouring. ### Textual materials You can create just a digital image, or a digital image and a machine-readable text. Determine in advance if blank pages will be scanned. Create images that meet or exceed these characteristics:
Printed texts and/or line drawings | 600 dpi, 1-bit
Grayscale, half-tone, and other black-and-white illustrations | 300 dpi, 8-bit
Color illustrated texts | 300 dpi, 24-bit
Rare/early printed texts | 300 dpi, 8- or 24-bit
Use Intel TIFF v 5.0 or 6.0 uncompressed or with lossless compression (ITU Group 4 for 1-bit or LZW for 8- or 24-bit). RGB or PhotoYCC are recommended as acceptable color spaces for digital masters. For machine-readable text, key in or use OCR text in ASCII, UTF-8, or Unicode, preferably corrected to at least 99.995% accuracy, and encoded (e.g., as specified in TEI Text Encoding in Libraries: Guidelines for Best Encoding Practices Version 1.0 (Digital Library Federation, July 1999). ### Pictorial materials Use these resolutions whether scanning from originals or intermediates:
Black-and-white photos | 400 dpi, 8-bit
Color photos | 400 dpi, 24-bit
Slides or small negatives | Effective resolution of 400 dpi, 8- or 24-bit
Use Intel TIFF v 5.0 or 6.0 uncompressed or with lossless compression (LZW). RGB or PhotoYCC are recommended as acceptable color spaces for digitalmasters. ### Audio Where these recommendations offer a choice, make your decision based on the nature of the original. For example, spoken-word conversion requirements are sometimes lower than those for other recorded sound such as music. However, an old music recording may not merit such high-quality capture as an excellent spoken-word recording.
Master file: 96 or 48 kHz; 24 bits | Bitstream: Uncompressed PCM Configuration: Monophonic or stereo depending upon characteristics of source item Sampling frequency: 96 or 48 kHz depending upon characteristics of source item, 24-bit word length (in some cases, 44.1 kHz/16 bit suffices) File format: WAVE Enhancement: none or as determined by contributor
Service file: MP3 (aka MPEG-1/2 layer 3 audio) | Bitstream: MP3 Quality: Data rate of 192 or 128 kilobits/second, as determined by contributor
### Motion
Master file | Component digital video bitstream (4:2:2 sampling rate) uncompressed. Note: the data rate for 4:2:2 is 270 Mbits/sec.
Service file | Compressed MPEG-2 files at pixel dimensions and data rates determined by contributor, possibly from a low of 1.2 Mbits/sec to a high of 15 Mbits/sec.
### Complex digital objects When digitizing component parts of an object, take care to maintain their relationships. For example, when capturing an album, consider, What is the relationship of the parts to the whole? Should each page be captured separately or should two pages be captured at once? Do the album pages have intrinsic significance, or is it sufficient to capture the images from each page? Is there a relationship between the spreads that should be maintained, or is an indication of sequence enough to recreate the experience of looking through the album? Provide structural metadata for complex digital objects to allow for navigation within the object. Preferably, use the Metadata Encoding Transmission Standard (METS). If you do not use METS, include a link in the record to the text file (if there is one), and a start image and end image. ### File naming Use file-naming schemes that are compatible across platforms and systems. Minimize the length of the name. Use only lower case characters a-z, numerical digits, and the following special characters: . _ - (period, underscore, and hyphen). Do not use spaces or any other special characters. Prefer a numbering scheme that reflects numbers already used in an existing cataloging system; if scanning precedes cataloging, use serial file names that will be incorporated into the catalog record. When developing a file-naming scheme, have a good understanding of the whole project. How many images will be scanned? Will they be stored in different directories? Are the files part of larger complex objects? Use standard file extensions (e.g., tif, .wav, .mp3, mpg, .rm, .txt., .sgm, .xml) in lower case only. Make sure the file references in your descriptive records match the file names (the extension may be omitted only if it is the same for every image.) The case of file references in the descriptive records must match the case of the actual file names. Replicate the directory structure as referenced in the descriptive records. Don't overload directories with too many files. Naming a collection of thousands of simple objects (e.g., a photographic collection) Subdivide them in a meaningful way (by series or group) or by chunk (same prefix or in groups of a thousand). Use the reproduction, accession, or a serial number as the stem of the file name. Add a code for special features: b for back, if scanning information on the back of a print d for a detail of a larger image Naming a complex object such as a book Create a directory for each object, using an identifying string for the object as the directory name. If there is a text file for the whole object (e.g., an SGML file), use the same string in its file name. For page image file names, use a sequential image number followed by the printed page number (when present), both with leading zeros, to fit the pattern "cccpppf", where: "ccc" is the image control number. These first three digits are used to assign a set of sequential numbers to all of the images for the book. The first image from the book is assigned control number 001; it reproduces the book cover. Control number 002 might be the illustrated end paper, 003 might be a title page, etc. depending on the book. If a document-start target is provided, scan it and give it the file name stem, 000000. If missing pages are encountered, scan a "missing page" target and assign the relevant control number. "ppp" is the printed page number. These next three digits carry the actual printed page number with leading zeros. If the number is Roman, provide the Arabic translation. If there is no printed page number, use 000. Assign a code for special features: g — Title Page (if the work has more than one, indicate the main title page) n — Table of Contents (if more than one page, indicate all pages) l — List of Illustrations (if more than one page, indicate all pages) f — Illustration (not a page image including an illustration, but an additional image cropped to include only the illustration) x — Index (if more than one page, indicate all pages) y — Missing page or other irregularity target Example: a book with the ID "mas 014" would be in a directory named mas014; it might contain these files: mas014/mas014.sgm mas014/000000.tif (target) mas014/001000c.tif (cover) mas014/002000.tif mas014/003000.tif mas014/003000f.tif (illus) mas014/004000g.tif (title page) mas014/005000.tif mas014/006000n.tif (contents) mas014/007000n.tif (contents cont.) mas014/008003.tif (first numbered page) etc. Naming a manuscript collection Create a directory for the collection, and subdirectories for each series, box, and/or folder. If there is a text file for the whole collection (or for each series, box, or folder) use the same string in its file name and place it in that directory. The page image file names will consist of a sequential image number with leading zeros. Since folders generally contain fewer than a thousand pages, you can use a three-digit number (including leading zeroes) for page-image naming. If a document-start target is provided, scan it and give it the file name stem, 000. Assign a code for special features: b for back side of a page s for start of a new document—since documents and pages are not equivalent, indicate when a new document (report, letter, etc.) begins by adding an s at the end of the file name for each image that represents the start of a new document Example: a manuscript collection with the collection identifier stw, would be in the directory stw, with the following subdirectories and files: stw/corresp/81/23/23.sgm stw/corresp/81/23/001s.tif (first page) stw/corresp/81/23/002.tif stw/corresp/81/23/003.tif stw/corresp/81/23/004s.tif (start of new document) stw/corresp/81/23/005.tif etc. stw/corresp/81/24/001s.tif etc. stw/reports/01/01/001s.tif etc. ### Submission Choose one of these methods: On media: ISO 9660 CDs or TAR on DLT. For RLG to pick up via FTP: provide access to the directory structure as referenced in the records. By FTP to RLG: copy the file directory structure referenced in records ### Sources METS: Metadata Encoding & Transmission Standard Official Web site Digital Library Federation, "Benchmark for Faithful Digital Reproductions of Monographs and Serials" (December 2002) Cornell University Library/Department of Preservation and Conservation, "Moving Theory into Practice: Digital Imaging Tutorial" (2000-2001) RLG, Digital Library Federation, "Guides to Quality in Visual Resource Imaging" (July 2000) Library of Congress, "Digital Audio-Video Repository System Support: Attachments to an RFQ, 5. Special Considerations For Digital Video and Audio" Digital Library Federation, "TEI Text Encoding in Libraries: Guidelines for Best Encoding Practices," Version 1.0 (30 July 1999) ## Recommended background for digitizing decisions Selection Outsourcing Cost estimating Imaging Text Audio Motion ### Selection Dan Hazen, Jeffrey Horrell, and Jan Merrill-Oldham, Selecting Research Collections for Digitization Council on Library and Information Resources, August 1998. (decision matrix) Selecting Library and Archive Collections for Digital Reformatting. Proceedings from an RLG Symposium Held November 5-6, 1995 in Washington, DC. ### Outsourcing RLG Guidelines for Creating a Request for Proposal for Digital Imaging Services (pdf) RLG, 1997 (May 1998). RLG Model Request for Information for Digital Imaging Services (pdf) RLG, 1997. RLG Model Request for Proposal for Digital Imaging Services (pdf) RLG, 1997. ### Cost estimating RLG Worksheet for Estimating Digital Reformatting Costs (pdf) RLG, 1997 (May 1998). ### Imaging Anne R. Kenney and Oya Y. Rieger, Moving Theory Into Practice; Digital Imaging for Libraries and Archives RLG, 2000 (see RLG Programs Books and Reports). Guides to Quality in Visual Resource Imaging Digital Library Federation (DLF) and RLG, 2000. Steven Puglia, "The Costs of Digital Imaging Projects", RLG DigiNews vol. 3, no. 5 (October 15, 1999). Imaging halftones: Anne R. Kenney and Louise Sharpe II, "Illustrated Book Study: Digital Conversion Requirements of Printed Illustrations", The Library of Congress Preservation (July, 1999). Imaging from microfilm: Louis H. Sharpe II, et al., Library of Congress Manuscript Digitization Demonstration Project Final Report October 1998. Selection, preparation, capture, metadata, archiving: Joint RLG and NPO Preservation Conference: Guidelines for Digital Imaging, September 1998. RLG Working Group on Preservation Issues of Metadata, Final Report RLG, May 1998. Franziska Frey, Digital Imaging for Photographic Collections: Foundations for Technical Standards", RLG DigiNews, vol. 1 no. 3 (December 15, 1997). Howard Besser and Jennifer Trant, An Introduction to Imaging, Getty Information Institute, 1995. ### Text TEI: The TEI Guidelines TEI, 2001. TEI Text Encoding in Libraries: Guidelines for Best Encoding Practices Version 1.0 Digital Library Federation, July 1999. Alan Morrison, Michael Popham, and Karen Wilkander, Creating and Documenting Electronic Texts: A Guide to Good Practice AHDS Guides to Good Practice, 1998. ### Audio Bruce Fries with Marty Fries, The MP3 and Internet Audio Handbook TeamCom Books, 2000: Chapter 11, "A Digital Audio Primer" and Chapter 12, "Digital Audio Formats" ### Motion Dave Anderson, The PC Technology Guide: Digital Video (2002). ## Digital conversion service bureaus RLG did not endorse these service providers, but received positive reports from those who had used them. Apex CoVantage ePublishing Solutions 120 Presidents Plaza 198 Van Buren Street Herndon, VA 20170 Phone: 703-709-3000 Fax: 703.709.0333 E-mail: info@apexcovantage.com Contacts: Margaret Boryczka or Tom O'Brien text conversion, SGML markup, EAD Backstage Library Works 1180 South 800 East Orem, Utah 84097 Phone: 800-316-2759 Fax: 801.356.8220 E-mail: jmoore@bslw.com Contact: Jodi Moore, Marketing Manager on-site/off-site scanning; text/prints/transparencies/realia; oversize; bound; data conversion; metadata processing; OCR Bar-Hama Blumenthal Digital Photography 450 Park avenue Suite 2702 New York, NY 10022 Tel: 212-400-3281 Fax: 212.400.3293 E-mail: ardon@barhama.com Contacts: Ardon Bar-Hama or George Blumenthal on-site, high resolution digital photography of rare books & manuscripts Boston Photo Imaging 20 Newbury Street Boston, MA 02116 Phone: 617-267-4086 Fax: 617.267.8711 Contact: David Sempberger photo scanning DCL Data Conversion Laboratory, Inc. 61-18 190th St., 2nd Floor Fresh Meadows, NY 11365 Phone: 718-357-8700 Fax: 718.357.8776 Contact: Shavy Schwimmer, convert@dclab.com scanning, OCR and text entry, SGML Direct Data Capture Ltd (UK and NY) 73 B Ormskirk Business Park New Court Way Ormskirk, Lancashire L39 2YT, UK Phone: 01695 570707 E-mail: brett@ddcltd.co.uk bound volume/microfilm scanning, text conversion Higher Education Digitisation Service University of Hertfordshire College Lane Hatfield, Hertfordshire AL10 9AB UK Phone: +44 1707 286078 E-mail: heds@herts.ac.uk digitization of all manner of originals Innodata Innodata Content Services Three University Plaza Hackensack, New Jersey 07601 Phone: 201-488-1200 Fax: 201.488.9099 Contact: Joan Meyer, joan_meyer@inod.com, or Steven Keyes, steven_keyes@inod.com, or Jan Palmen data aggregation and conversion, XML transformation, OCR, and image scanning Input Solutions, Inc (ISI) Gaithersburg, MD Phone: 301-948-6620 Contact: John Solomon scanning and conversion, microfilm, oversize, text, SGML JJT, Inc. Corporate Headquarters, R&D & Production Center 26 Howland St. Plymouth, MA 02360 Phone: 508-747-9889 Fax: 508-747-9289 Email: info@jjt.com JJT, Inc. New York Production Center 231 W. 29th Street Suite 701 New York, NY 10001 Phone: 212-594-5106 Email: atroncale@jjt.com Contact: Anthony Troncale high-quality digital reproductions of pictorial works, including line and photographic images and manuscripts; specializing in conversion of large collections Kirtas Technologies, Inc. 7620 Omnitech Place Victor, New York 14564-9782 Phone: (585) 924-2420, ext. 3008 E-mail: mmaxwell@kirtas.com Contact: Michael Maxwell, Director of Worldwide Sales Non-destructive, high quality, inexpensive, bound document scanning (on and off-site) of books, journals, magazines, lab notebooks, etc. with OCR and metadata capture capabilities Luna Imaging, Inc. 3542 Hayden Ave., Bldg. One Culver City, CA 90232-2413 Phone: 310-452-8370 Fax: 310.452.8389 E-mail: sales@luna-img.com film and print scanning, direct digital photography, image editing and post-production, on-site services, image studio/workflow consulting Northern Micrographics 2004 Kramer Street LaCrosse, Wisconsin 54602 Contact: Tom Ringdahl, tringdahl@normicro.com scanning from paper or film Preservation Resources 9 Commerce Way Bethlehem, PA 18017 Phone: 800-773-7222 or 610-758-8700 Fax: 610.758.9700 Contact: presres@oclc.org microfilm scanning Saztec International 6700 Corporate Dr. Kansas City, MO 64120 Phone: 816-483-6900 Fax: 816.241.4966 text conversion, SGML Systems Integration Group, Inc. 9701 Philadelphia Court Building 17, Suite A Lanham, Maryland 20706 Phone: 301-731-3900 Fax: 301.731.3907 on-site/off-site document scanning, text conversion, SGML Two Cat Digital, Inc. 14717 Catalina Street San Leandro, CA 94577 Phone: 510-940-2670 Fax: 510.940.2632 Contact: Howard Brainen, howard@twocatdigital.com film and print scanning, direct digital photography, image editing, bulk image processing services, automated systems, image databases, on-site services, digital imaging consulting ## Suggestions if you've already created your digital surrogates The following were suggestions for the quality and format of the files already digitized. These were not requirements. 2D images Text Audio and motion ### 2D images Formats and compression: In general, you'll probably want to keep a TIFF (Tagged Image File Format, version 5 or 6 with Intel headers) version of the image with lossless compression (ITU 4 for black and white or LZW for grayscale or color) or no compression, but a JPEG compressed image will suffice for contribution to RLG Cultural Materials. Alternatively, PhotoCD images may meet your local needs, and JPEGs can be created from those images for contribution to RLG Cultural Materials.
Source | Resolution
--- | ---
Black-and-white text and line art | 300-600 dpi bitonal
Halftone illustrations | 300-400 dpi, 8 bpp or 24bpp
Oversized (e.g., maps or posters) | 300 dpi bitonal, 8 bpp or 24 bpp
Manuscript page images | 300-400 dpi, 8 bpp (24 bpp for color, tinted, or discolored originals)
35mm photographic negatives or slides (reverse polarity if negative) | 3000 pixels in long dimension, 8 bpp or 24 bpp
Photographic prints and transparencies (4x5, 6x8, 8x10) | 4000-6000 pixels in long dimension, 8 bpp or 24 bpp
### Text
Source | Quality | Format | Encoding (optional)
--- | --- | --- | ---
Printed page (OCR or rekey) | 99.95% accuracy as compared to original | ASCII 7- or 8-bit | HTML, XML, SGML, RTF
Compound document, in Portable Document Format (PDF) | Text and images as indicated above | PDF |
### Audio and motion Formats and compression: Any of these are acceptable: Microsoft Wave (.wav), MPEG (.mp3, .mpg, .mpeg), "Audio Video Interleave" for Windows (.avi), QuickTime (.qt, .mov), RealMedia (.rm, .ra, .ram).
Source | Quality
--- | ---
Spoken word | 11-22 kHz sampling, 16 bit, mono
Music | 44.1 kHz sampling, 16 bit, stereo
Video | 320x240 30 fps/1.2kbps