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Unit 1, 10 Surrey street
PO Box 51248, Tawa
Wellington 5249
P:+64 4 232 9396
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Preparation for digitisation

What will you do with the images?

HMIF abides by the Digital Imaging Best Practices as devised by the Bibliographical Center for Research's  Collaborative Digitization Program. For more information on these guidelines, a pdf file is downloadable from here.

It is extremely important to be clear about the aim of the digitisation before commencing the project. Common purposes for digitisation could include research, to enhance preservation of the original, for intranet access or for reproduction purposes.

The most common purposes however, tends to be a combination of these goals, which can make a digitisation process complex. Therefore you will need to establish what quality of files you will need, and any derivatives required thereof.

For example, the Rossdhu Book of Hours was supplied in multiple formats:

  • Original Master Image for high level research, reproduction - 600ppi RGB TIF @ actual size - allows viewing at up to six times actual size without pixelation (105MB file)
  • Derivative Image for quick printout - 300ppi RGB jpeg maximum quality - allows viewing at up to three times actual size without pixelation (7MB file)
  • Derivative Image for viewing in an intranet environment, possibly library - 96ppi RGB jpeg maximum quality (2.5 MB)
  • Derivative Image for viewing in an online environment, e.g. internet - 96ppi RGB jpeg medium quality (200Kb)
  • Acrobat PDF file created from option 4 images - possible download from internet or distributed on CD.

Once you have decided on what role your digital images will serve, the digitisation technology can be arranged for the needs of the process. The setting contains mostly the same components for each project, but can change in order to serve the needs of special materials or formats.

The HMIF normally recommends scanning at very high (highest possible) quality to maximise the reproduction possibilities and give greater flexibility in creating derivatives. This also reduces the risk of having to re-digitise as capture technology improves.

Check your book before starting

If possible, the original should be examined in a safe place away from the digitisation environment. It is considered very valuable to seek cooperation with curators, conservators or experienced research people who can give specialised comments on important and relevant issues regarding materials handling and their impact on the objects during the digitisation process.

A condition report before digitising commences is invaluable as it can point out potential handling difficulties which can arise during the digitisation process, avoiding potential damage to a unique piece. There was a condition report prepared for the Rossdhu Book of Hours prior to us receiving the book. This report should also consider transport of the volume to the scan facilities. We also received advice on handling the from the curator of the Special Collections at Auckland City Library, and the National Preservation Office, as well as professional advice from conservator of Works of Art on Paper Marion Mehrtens, and book conservator David Ashman from Triptych Conservation Services. With the help of all these organisations and David Ashman we conducted our own condition report for the purposes of digitisation.

Our book report concentrated particularly on interesting aspects of the book which would affect the handling and digitisation requirements, i.e. how much we could open the book and the inability of the pages to lie flat (buckling). Of particular interest to us were areas where the vellum had worn particularly thin and fragile.

We decided on the following techniques for minimising digitisation difficulties while ensuring primary attention was to the handling requirements of the book:

  • Due to the age and delicacy of the book it could not be handled using bare hands. Gloves were used at all times when handling the book. We used cotton gloves. This required extra concentration when moving the book from its storage enclosure to the camera as the leather-bound cover of the book was slippery. To minimise this problem, we used a setup table on wheels which could be moved to as close to the scanner as possible to ensure minimal carrying of the book.
  • Not unexpectedly, we experienced varying degrees of thicknesses in the vellum pages, in no particular or logical sequence and careful examination of each page before handling was crucial to reduce risk of damage to the thinner and more fragile pages. The Index pages were noticeably worn and thin through "thumbing" and required special attention during page handling.
  • The maximum the book was able to be safely opened was 110° - 120°. This meant we had to use an angled book cradle and digitise one side at a time.
  • The pages of the book had to be allowed to sit without risk to the spine - there could be no undue pressure used to hold them flat. This meant that depth of field could become an issue.
  • When turning the pages we chose to use a combination of paper triangles made from acid-free paper and bones made from Teflon. Hands were washed regularly and thoroughly, and gloves were regularly refreshed.

The final step in our preparation was to run tests of our handling methods using a "dummy" book of the same size. This meant we were able to practice and refine our techniques without risk to a precious book.

The Room environment

Our facilities in the National Library of New Zealand building are maintained at a constant 22° C in winter and 23° C in summer. The humidity is kept at a constant 40%. Lighting is kept at a low level and we use daylight 5500°K fluorescent lighting. There are no lights around the scanner. There are no windows in this room. The walls are painted a neutral shade of gray to avoid colour casts from the ambient environment affecting the look on the screen. We have used industrial linoleum on the floor and positive air pressure supplied by the air conditioning is utilised to ensure the room remains as dust-free as possible. Thorough cleaning of the prep area, scan bed/book cradle and materials likely to come into contact with the book was undertaken. The optics were also cleaned before commencement of scanning. We also thoroughly vacuumed the area around the scanner to minimize any dust.

The Camera

For the digitising of the Rossdhu Book of Hours we used our Cruse digital scanning camera. The Cruse CS 185SL450 Synchron Light scanner is designed to be as noninvasive as is possible. The CS 185SL450 has the 450MB head, which enables a scan of 10,000 x 15,000 pixels to be performed. A wide variety of accessories are available to meet any scanning needs, from postage stamp size through to large format.

With options including both 180° and 90-180° book cradles and a large copy board which can handle three-dimensional objects with a depth of up to 100mm, making it particularly suitable for scanning artwork that cannot be removed from frames, we are able to digitise everything from the most delicate to extremely robust articles, at original sizes never before possible in Australasia.

The Cruse scanner relies on a complex software algorithm to achieve extremely accurate focus for all scanner setups. Since the Cruse scanner does not utilise a focus knob or ground glass, no element of human error is introduced, ensuring maximum sharpness on all scans. The Cruse camera utilises cold-cathode lighting which imparts almost no heat at the object.

We have modified the lighting to bring UV levels to <45 microwatts/lumen using UV-reducing gels, ensuring there is minimal UV interference with the book. In order to keep lux levels down, the book was covered with light reflecting cloth during any time it was not being either scanned or handled.

Preparing the Camera

The Cruse scanner software allows us to create "job profiles" for each particular job we embark on. This allows us to tailor the characteristics of the scanner to suit the job and then store all these settings in the program to be recalled at any particular time.

For the purposes of this digitisation project we saved the following settings:

  • Lens F-stop
  • CCD Sensitivity
  • Integration Time
  • Size of the Book
  • The height of the page to be digitised (focus)
  • Input and Output resolution (Pixels per inch)
  • Magnification Rate
  • Pixel Resolution
  • The folder to save the files into

All of these settings were established with a dummy book under the camera, to ensure that not only did we have the opportunity to practice and refine our handling technique without any extra handling of the book to be digitised, but that we also subjected it to the least amount of ultraviolet and lux light.

Materials used to facilitate digitisation

We used the following objects to help us hold and support the book:

The angled book cradle was used with various closed-cell plastizote foam sheets placed on top of the cradle to raise the height of the digitising area. On top of this was added black cloth and finally, unbleached wash calico cloth (to cover the book cradle)

We used snake weights (curtain leads encased in unbleached washed calico) to hold back the top pages of the book. We used Bulldog clips to hold back snake weights at the back of the book cradle.

Teflon bones and mylar strips held down with tri weights (lead shot encased in black polar fleece fabric) were used to hold down the horizontal pages, while black and white closed-cell Plastazote foam was used under the pages to keep them as horizontal as possible.

Colour Calibration and Profiling

It is absolutely essential to ensure that the colour of the object being scanned is the colour that the end user will see. To ensure that this is accurate we used a combination of ICC profiling and colour calibration devices to ensure monitor calibration. We used Pantone Colorvision's OptiCal software in combination with their Spyder calibration tool and latterly the Gretag Macbeth Eye-One to ensure that our EIZO Flexscan S1910 19 inch LCD monitors on our computers were accurate. The screens are set to a daylight colour space where white = 5600°K. The monitors were then calibrated to this standard using OptiCal which create ICC monitor profiles for the operating system software (currently Windows 2000 Professional SP4).

To ensure accurate colour at the scanner we performed extensive black and white calibration routines which entered the white and black figures into the scanning software database. This way the scanning software knows the ultimate white and black values. This was done using a program which comes with the scanning software. The black values on the CCD were performed by putting the lens cap on the scanner and running a program which checks the entire CCD array using an 8 x 32 pixel grid. The white values on the CCD were performed by placing a large sheet of white unbranded photographic paper on the scanner and running a program which checks the entire CCD array using an 8 x 32 pixel grid. These calibration values are checked at varying enlargements so the scanning software has a database matrix allowing it to know the black and white values at any magnification at any point on the scanner to a very accurate level. During setup of the scanner this process can take several days.

Once the absolute black and white values for the scanner are determined, we scan icc profiling targets. For our scanner we chose the Kodak Professional Q-60 IT-8 Colour Input target (Kodak cat. No 190 7914 batch 2002:11). This IT-8 target contains 264 known colour values plus a 24-step greyscale step wedge on a reflective photographic paper. Once the target is scanned, it is imported into an ICC-creating program. We used Heidelberg's ScanOpen ICC, although there are a number of excellent programs out there. The scanned target is compared to a file which has the correct RGB values for that particular batch and an ICC profile is created.

Rather than increase the file area and incorporate the Q-60 in every image, we chose to check the Q60 target every morning , and up to 6 further times during the day, particularly after breaks.

An ICC profile tells the scanner how a colour it "sees" should be interpreted in the TIFF file. A TIFF file can "carry" an ICC profile which can be "read" in conjunction with the TIFF file when it is opened. Adobe Photoshop can open files with ICC information intact and is recommended for viewing master images.

Computer Equipment

Digitally scanned files are large. The amount of disk space taken up can be extremely large and if you want to accurately work with these images you will need quite powerful equipment.

Our scan software runs on a Windows™ Platform. Our QC software runs on an Apple Macintosh Platform. There are no specific advantages to using either platform for QC, and we have run and still do run Windows PCs for QC.

Our scanning computer has the following specifications:

2.53Ghz PENTIUM4™ on Intel motherboard

2048MB RAMBUS RAM

2 x 120GB 7200rpm IDE drives, running RAID0 (mirror) through PROMISE hardware RAID, giving 1 x 120GB drive

Nvidia Quadro4 750XGL 128MB videocard.

Samsung SM-348B combination DVD Reader/CD Writer

Windows™ 2000 Professional SP3

Cruse CSX 1.0

Adobe Photoshop 7.1

Our quality control computer has the following specifications:

Apple Macintosh G5 Dual 2.2 Ghz CPU

4096MB DDR400 RAM

2 x 250GB SATA hard drives

Nvidia GeForce FX5600 256MB videocard.

Pioneer DVR-A05 combination DVD Writer/CD Writer

MacOsX 10.4

Adobe Photoshop CS2

Adobe Acrobat 8.0

Both computers use EIZO Flexscan S1910 19 inch LCD monitors, which are calibrated through ICC profiling and Gretag Macbeth Eye-One hardware and software.

Our computers run on a 1000Mb Ethernet network, using Cat-5e ethernet cable and a combination ADSL/ethernet router, which provides both a DHCP hub and firewall, and access to the outside world via ADSL.

Backup services are provided by both DVD/CD writing and DLT tape.