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Franziska Frey 2 / DHV13
 

Franziska Frey 2 / DHV13

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    Franziska Frey 2 / DHV13 Franziska Frey 2 / DHV13 Document Transcript

    • 10/7/13 1 Preservation Strategies for Digital Image Collections Franziska Frey" Malloy Rabinowitz Preservation Librarian" Head of Preservation and Digital Imaging Services" Harvard Library Requirements To Make Digital Work •  Deep and longstanding institutional commitment to traditional preservation •  Full integration of technology into information management procedures and processes •  Significant leadership in developing appropriate definitions and standards Responsibility •  “Digital preservation will only happen if organisations and individuals accept responsibility for it. •  Acceptance of responsibility should be explicitly and responsibly declared…..”" " UNESCO, “Guidelines for the Preservation of Digital Heritage,” 2003 Control •  Move objects to a safe place •  Uniquely identify and describe images with appropriate metadata for resource discovery, management, and preservation •  Use standardised metadata schemas for interoperability •  Ensure that links between digital objects and their metadata are securely maintained, and that the metadata are also preserved." " UNESCO, “Guidelines for the Preservation of Digital Heritage,” 2003 Stewardship •  Long-term management of heritage materials (digital objects) through collaboration, throughout all phases of object life cycle. – Rights holders – Collection managers – Repository/preservation staff – Centers of expertise (researchers, scientists) – Auditors – Content users and their communities
    • 10/7/13 2 Stewardship ─ Collection" Manager’s Responsibilities •  Intellectual property rights: manage legal rights, including rights to make copies •  Metadata: provide appropriate administrative, technical, and structural metadata for objects •  Discovery: ensure that description of objects are publicly available in online discovery systems •  Access: ensure that a version of the object is available to the Harvard community •  Financial considerations: pay for repository and preservation services" " Harvard University Library, DRS Policy Guide Techniques to Preserve Images •  Phase 1―Production •  Phase 2―Appraisal •  Phase 3―Deposit •  Phase 4―Archiving and Preservation •  Phase 5―Discovery and Delivery Phase 1 ― Production" •  Imaging does matter •  Formats do matter •  Documentation does matter Art-si.org Image Quality Matters •  High quality images can be repurposed and are worth maintaining •  Steve Puglia: ”We feel that the managed environment needs to be extended beyond the digital repository and forwarded in time to include the digitization process….”" (IS&T Archiving Conference, 2008) Building Teams •  Preserving visual cultural heritage materials involves one additional field: Imaging Science – It is imperative that the person involved in creating these materials, whether born digital or digitized, has a good knowledge of imaging
    • 10/7/13 3 Consequences of These Decisions" Vis-à-vis Preservation •  Resolution – As size increases (e.g., decisions to capture and keep 48 bit, high resolution files), management overhead increases •  This holds true especially if the storage unit bills per MB or GB per year How are Digital Libraries Evaluated? •  Almost no research on implications of image quality •  User interfaces and usability in terms of finding the right image have been evaluated •  Why this gap? –  Do users know what they can demand in terms of image quality? •  Visual literacy –  Image quality studies are complex and expensive Reproductions of Cultural Heritage Materials Needed for… •  On-line databases •  Posters, calendars, and postcards •  Exhibition catalogues •  Education •  Conservation •  And more Survey—Imaging Purposes To protect vulnerable originals from use 67% To produce printed reproductions 77% To make collection accessible over the Internet 86% To include in a collection management system 86% To document conservation treatment 58% Other 28%
    • 10/7/13 4 However… •  Reproducing cultural heritage materials can be difficult –  Color and texture –  Printing may be taking place half a world away •  It is of interest to limit the number of times an artwork is imaged –  Potential for damage to the artwork –  Expensive •  Resources are limited –  Budget cuts –  Many institutions do not have dedicated reproduction departments Viewing Conditions •  Reproductions are viewed under various lighting conditions… – Museum shop, living room, class room – Displays •  …even for image evaluation – Light booth, gallery, office •  Significant issues – Metamerism – Color appearance – Consistency Project Objectives •  Determine the optimal reproduction processes presently available –  Understand the workflow processes in use in cultural heritage institutions today –  Determine the image quality inherent in these processes in print and on line –  Understand the image quality expectations of the users involved •  Develop a framework to serve as a guideline for cultural heritage institutions to follow when reproducing fine art ImageMuse •  Establish a user group devoted to imaging, archiving, and reproducing cultural heritage •  17+1 institutions took part in our experiments Image Quality Metrics •  Document current workflows •  Develop a practical characterization test method: industry solutions •  Document available targets to measure objective image quality Workflow Charts Capture Illumination Camera Post-Processing Proofing Further Processes
    • 10/7/13 5 Documented Reproduction Workflows Workflow Process General Function Specific Workflow Process Steps and Considerations Additional Steps and Considerations 1. Image capture Objective targets used Lighting set up used to illuminate the artwork including polarization Camera calibration Flat-fielding 2. Proofing and image file preparation Monitor Calibration Working color space Screen background used for file viewing Viewing environment Physical image size on the screen Sharpening Image orientation Resolution and file size 3. Image delivery File format Image layers for documentation of image processing conducted ICC color management Delivery media Guide prints and proofs 4. Image archiving Archiving protocol Proper handling and storage of guide prints Metadata Image naming Hidden-Target Paintings Gamblin Artist’s Oil Colors Comparison of Corrected Paintings CS1 CS2 CS3 CS4 Universal Test Target Results from UTT Cameras—Color Performance
    • 10/7/13 6 Objective Targets •  Input targets—output targets Experimentation •  Define quality criteria based on objective and subjective metrics •  Develop a method to connect objective, measurable image quality to subjective image quality as perceived by the observers •  Benchmark current quality Subjective Targets Press Sheets Experimental Methodology •  Emphasis on the perceptual image quality of printed reproduction and on display – Objective targets measured as well •  Evaluation performed using a variety of pictorial “targets” – Sent to a variety of cultural heritage institutions for them to put through their imaging processes
    • 10/7/13 7 Images Printed at RIT’s Print Applications Laboratory •  Heidelberg Speedmaster sheet-fed press – ISO 12647 – Visual match to guide prints – NewPage Sterling 80# Gloss Text •  HP Indigo Digital Press Perceptual Testing •  Observers experienced with fine art reproduction –  Fine art photographers –  Curators –  Art historians –  Conservators –  Librarians –  RIT students & staff Experiments Conducted •  The Impact Of Lighting On Perceived Quality Of Fine Art Reproductions •  Evaluating CATs as Predictors of Observer Adjustments in Softcopy Fine Art Reproduction •  Comparing Hardcopy and Softcopy Results In the Study of the Impact of Workflow on Perceived Reproduction Quality of Fine Art Image •  Evaluating Digital Printing for Fine Art Reproduction •  Fine Art Reproduction Workflows for the Web Environment Objective Targets Experimental Methodology •  17 institutions participated •  30 hard-copy renditions of each of image were included – 19 prints made ‘to the numbers’ – 11 visual matches made to guide prints •  All prints made on NewPage Sterling Ultra 80# Matte Text paper •  16 soft-copy renditions used •  Variety of cameras and color spaces
    • 10/7/13 8 Psychophysical Testing •  Hard copy experiments followed rank order protocol –  Observers ordered the prints from best to worst reproduction or representation of the original –  Most to least preferred rendition •  Soft copy experiments followed paired comparison protocol –  Best reproduction or representation of the original –  Most preferred rendition Soft-copy set up Hard-copy set up Experimental Setups Key Findings •  Results with and without the original present are more consistent for hard-copy prints than soft-copy images •  Hard-copy results are more consistent with soft-copy results when the original is present –  Original is typically not present when users are viewing fine art reproductions •  Observers did not like lower contrast images when they were electronically displayed •  Of interest to identify workflows that provide both acceptable representations of the originals as well as pleasing images on screen and in print Color Difference (ΔEab) at Capture Lightness Difference (ΔL) versus" Perceptual Quality Rating (Z-score) R 2 = 0.8144 0 2 4 6 8 10 12 -1 -0.5 0 0.5 1 Mean Z-scores MeanDeltaL Mean Delta L Form 5 Form 11 Form 13 Form 19 Linear (Mean Delta L) Experiments Conducted •  The Impact Of Lighting On Perceived Quality Of Fine Art Reproductions •  Evaluating CATs as Predictors of Observer Adjustments in Softcopy Fine Art Reproduction •  Comparing Hardcopy and Softcopy Results In the Study of the Impact of Workflow on Perceived Reproduction Quality of Fine Art Image •  Evaluating Digital Printing for Fine Art Reproduction •  Fine Art Reproduction Workflows for the Web Environment
    • 10/7/13 9 Color Management Check Web Experiment User Interface Key Areas of Interest Key Areas for Photographers versus Other Occupations Key Findings •  Testing conditions had a limited impact on the preference judgments for these images •  Ranking results for the experiments conducted in the lab without the original and via the web were highly correlated, indicating that, when the original is not included, a web-based test may be a reasonable approach Key Experimental Findings •  Camera make, lights, file format did not influence our results –  Everybody is using equipment uniformly capable of doing this job •  Lighting conditions may have a strong impact on image appearance –  Proofing protocols will have to be revisited •  The use of a target to ensure proper capture setup is recommended •  Main goal: get the tone scale right at capture •  Following standardized workflows, ISO printing standards and viewing standards reduces need for manual post processing
    • 10/7/13 10 Key Findings−Interviews •  Define imaging goals and talk to your users – This will help set expectations •  Acceptability varies for the different stakeholders – this needs to be clearly communicated •  Document workflows in detail –  No undocumented processing should be performed along the image interchange cycle –  The more often a file is touched the worse the results •  Close the communication loop in the image interchange cycle Art Image Interchange Cycle Photographers Paper Manufacturers Conservators Publication Staff Curators Printers Visitors Imaging Scientists Standards Experts Graphic Designers Managers of Imaging Studios Art Historians DAM staff Equipment Manufacturers Digital Imaging Specialists Licensing Staff Exhibitions Editorial Pre-press Merchandising Librarians Metatorial Future Work •  Standardization even more important with globalized workflows –  ISO JWG 26: combining existing guidelines and standards for quality evaluation of imaging systems –  Training for implementation of standards needed –  Define stepping stones to get to a standardized workflow •  Bring all threads of imaging in an institution under “one roof” Techniques to Preserve Images •  Phase 1―Production •  Phase 2―Appraisal •  Phase 3―Deposit •  Phase 4―Archiving and Preservation •  Phase 5―Discovery and Delivery Phase 2 ― Appraisal •  Deciding what is essential – Characteristics that give object meaning, integrity, authenticity •  Encode what is essential – Metadata production •  Validating objects – Are they what they seem to be? Checksums Metadata •  Descriptive –  You cannot preserve what you do not know you have –  You cannot sustain use for items that cannot be identified •  Structural –  Encoding of relationships facilitates management, use •  Administrative –  Ownership, rights of access, provenance •  Technical/Preservation –  Format attributes –  Documentation of significant properties and preservation intentions to inform preservation strategies
    • 10/7/13 11 www.loc.gov/standards/premis/" v2/premis-2-0.pdf Metadata Containers •  Directory and file names •  File headers •  XML – XMP (e.g., within JP2), EXIF, NISO MIX, METS •  Database tables •  Printed reports NISO Phase 3 ― Deposit •  Choosing a repository: build or buy? •  Packaging data for deposit •  Validating data and objects Phase 4 ― Archiving and Preservation •  Repositories •  Standards and guidelines Storage Options •  Interim storage – Digital asset management system – Store data off-line on magnetic or optical media •  Repository storage – Build a repository – Pay annual fee to use an external repository
    • 10/7/13 12 Interim Storage─The Bare Essentials •  Assign checksums to images early in the production process •  Document rationale for creating images –  At very least, include read me file on storage media; database is best •  Avoid use of “meaningful” filenames •  Use new media –  Follow advice/recommendations of IT9.21 and IT9.23 standards •  Create duplicates and store duplicates in separate locations •  Create explicit “links” between catalog records and images •  Assign preservation responsibility to appropriate entity Preservation Repository •  Long term storage strategy for masters – Preservation responsibilities delegated to service provider – OAIS – Accountable, auditable and fiscally sustainable Managing Risk •  Security and access control – Preventing unauthorized use, tampering or theft – Protecting rights holders •  Data obsolescence – Media incompatible with players – Formats •  Functional obsolescence – Formats incompatible with user needs •  Fiscal obsolescence Phase 5 ― Discovery and Delivery •  Digital library infrastructure – Catalog or other database for descriptive information – Persistent naming – Access management •  Rendering – Hardware, web browsers – Emulator Pricing Components" •  Various pricing models – Subscription (JSTOR) – Storage (Harvard Digital Repository Service) – Accession, subscription and storage (OCLC Digital Archive) Managing Costs •  Minimize number of conservation and reformatting interventions over entire life- cycle •  Manage the storage environment – “Geography is preservation destiny” •  Negotiate costs of outsourced services, e.g., through consortia
    • 10/7/13 13 Summary •  Digitization is not preservation •  Storage is not synonymous with digital preservation, and storage is neither free nor cheap •  Stewardship and digital preservation require active oversight of content, technologies, and user expectations •  Preservation planning depends and relies upon extensive, well-managed metadata •  Distributed, but shared expertise centers and tools will be essential to managing costs Acknowledgements The Andrew W. Mellon Foundation Participating Institutions Susan Farnand, RIT Observers Steven Chapman, Harvard University