THE BRITISH LIBRARY

Collection Care blog

5 posts from December 2013

31 December 2013

New Year’s Resolution: 300 ppi?

Did you know that image resolution has absolutely nothing to do with how an image looks on a screen? It is a fairly safe bet that more of our collections will be digitised in the next few years. As technology moves on with great pace there is often debate as to the “best resolution” that images should be captured at. But what does that actually mean? This post will try to explain what is meant by the terms pixel and image resolution, and will demonstrate the relationship between them.

Pixels and megapixels

Digital images are made up of thousands or even millions of pixels (picture elements). A pixel is the smallest addressable element in a display device with a specific assigned value that can be read by a computer and mapped onto a grid to recreate an image. Each pixel is a sample of an original image, so the more samples available result in a more accurate representation of the original. We can change the appearance of an image by manipulating the pixels or by getting rid of some of them to reduce the file size. Below we see a digital image of the Gospel of St John from the Lindisfarne Gospels (British Library, Cotton MS Nero D.IV). It is obvious that the image on the left with more pixels is of a higher quality than that on the right.

Unpixelated  Pixelated
CC by The image with more pixels produces a more accurate representation of the subject matter. The image on the right looks “pixelated” due to the visibility of the pixel boundaries

How pixels control resolution

Pixels control image resolution because the closer the pixels are placed (i.e. the more there are per inch), then the denser the image becomes with detail. Similarly, the fewer pixels an image has per inch, the further apart they are spaced, resulting in less detail and an image of poor quality.

Image resolution is therefore concerned with the number of pixels per inch (ppi) printed out on a piece of paper, and the size of those pixels. Since the software takes care of the pixel size, it’s really just the ppi that you need to think about.

Let’s try to understand that better by taking a look at an image captured with a DSLR camera. Below is a photograph of our new multispectral imaging system opened in the open source image processing software package ImageJ.

Screen shot of open image

CC by Fullsize, uncompressed image opened in ImageJ

If we look at the title bar of the image we can see some details about the image file.

Screen shot of open image title bar

CC by The title bar tells us the name of the image file, the percentage size in brackets, and the number of pixels

The title bar (DSC_0074.JPG (16.7%)) tells us that this file is only opening up to 16.7% of full size. The image is just too large to open on the screen at 100%. Below the title bar we can also see that the size of the image is 6,000 x 4,000 pixels (i.e. there are 6,000 pixels running along the image from left to right and 4,000 pixels running from top to bottom). That sounds like a lot of pixels. If we now zoom in on any part of the image we can see these pixels as little squares of colour.

Zooming in  Zooming in  Zooming in
CC by As we zoom in on the image it becomes apparent that it is made up of pixels

If there are 6,000 pixels along the top of the image, and 4,000 pixels along the side, then my incredible math skills suggest that there must be 24,000,000 (= 4,000 x 6,000) pixels in total, or 24 million pixels, or 24 megapixels (MP). A quick glance at the camera manual will show that this camera (Nikon D5200) has in fact got a 24 MP CMOS sensor, so our powers of deduction are correct.

Resolution doesn’t mean anything until you go to print

We now know that there are 6,000 x 4,000 pixels in our image. Great! But what does that mean if we want to print out this image on a piece of paper? How does a pixel correlate to the size of the page? Will the image fill the whole page or will it just appear as a tiny thumbnail? Take a look at the image resolution by opening the image up in another great open source image processing package called GIMP, and opening the Set Image Print Resolution window.

Set Image Print Resolution

CC by Open the image in GIMP and navigate to the Set Image Print Resolution window

Here we can see that the X and Y resolution is 300 pixels/in which means that that for every inch of paper we have, there will be 300 pixels printed. So if we have 6,000 pixels along the top and 4,000 along the side that means we must have 6,000/300 = 20 inches along the top and 4,000/300 = 13.333 inches along the side… and if we look at the print size in the window above we can see that has already been calculated for us.

20 by 13+ inches is quite a large size. How can we print it out smaller to fit on our page? We need to fit more pixels into each inch, and since the size of an inch can’t change then the size of the pixels must change. That is done automatically for us by GIMP or Photoshop, or whatever image processing software package you are using. Let’s say we set our image resolution to be 600 pixels per inch. In that case we can see that the print size has adjusted to a much more manageable 10 x 6.67 inches. The resolution changes as the physical image size changes because the number of pixels that make up the image are being spread over a greater or lesser area.

Set Image Print Resolution

CC by By increasing the number of pixels per inch we can fit our image into a smaller area of the page

PC monitors are generally considered to be low resolution devices meaning that images look good on screen even if they have a very small total number of pixels. This reduced number of pixels also allows images to load faster leading to an overall better user experience. But if you try to print it out, you may be disappointed at the tiny image that emerges from your printer. Printers are high resolution devices and require an image to have a resolution of about 300 pixels per inch to look sharp and to be of a good quality. 300 ppi is generally accepted as the resolution for professional quality printing, but that number is increasing all of the time. There are many great articles and tutorials about this and other aspects of digital objects found on the Digital Photo Essentials Tutorial for anyone new to the world of digital photography or photo-editing.

Best of luck with your New Year's Resolutions!

Christina Duffy (@DuffyChristina)
Imaging Scientist

22 December 2013

New hyperspectral imaging capabilities at the British Library

Collection Care has excitedly accepted delivery of a new hyperspectral imaging system. The system is designed specifically for archival and cultural heritage imaging for the purpose of revealing hidden and faded information. Digital imaging experts MegaVision, who are based in California, design the system. The EVTM camera includes MegaVision’s Monochrome E7 50-megapixel back, computer controlled shutter and aperture, and custom hyperspectral parfocal lens, which is responsive over the entire range of silicon sensitivity.

MegaVision system
  CC by 
Testing of the MegaVision Cultural Heritage EVTM Imaging System showing LED sidelights with diffusers, and the E7 50 MP digital camera back on vertical mount

The system integrates two previously disparate imaging capabilities: high-resolution photography and multi-spectral imaging. Images are captured over 12 spectral bands from the near ultraviolet (365 nm) to the near infrared (1050 nm). Captured images are used for preservation and scholarly studies of British Library collections on materials such as parchment, paper, papyrus, inks and other constituents of cultural items. A series of palimpsests (parchment from which writing has been erased and overwritten) and Treasures of the British Library have been identified for imaging, which will take place in the New Year.

  Palimpsest

CC by Evidence of palimpsest detail under UV illumination in this Syriac manuscript (OMS Add 14623)

The MegaVision system replaces the Forth Photonics MuSIS system, which was purchased in 2004 for work on the Codex Sinaiticus project, and has found many applications since. MuSIS creates spectral bands using band pass filters to filter the light after it is reflected from the collection item. The MegaVision system uses narrow-band LED illumination, which subjects the collection items to only the required light energy to expose the sensitive unfiltered monochrome sensor. The LED panels are configured with visible, UV and IR bands. This selective illumination process significantly reduces the light energy falling on collection items, and has the added bonus of looking very cool indeed!

Green light

CC by Green illumination: Narrow-band LED illumination subjects collection items to different light wavelengths (red, green, blue, cyan, amber, UV, IR)

MegaVision's PhotoshootTM digital image capture software controls all aspects of capture as well as controlling a colour wheel which allows additional light modifications such as filtration to isolate fluorescene in concert with UV illumination.

The technology has been internationally heralded for its use on the Archimedes Palimpsest Project, the Gettysburg Address and the Waldseemüller map, while data is still being captured from St Catherine’s Monastery in the Sinai Desert. The datasets will become digital assets of historical and scientific value in their own right, and can be further processed to enhance regions of interest.

This is a landmark purchase for Collection Care showing the committment we have to furthering the understanding of our collections and the importance of science and research in archival institutions. The quest for information recovery and discovery continues! 

Christina Duffy (@DuffyChristina)

Imaging Scientist

19 December 2013

Supporting the UK digital preservation community through SPRUCE

The Library’s digital preservation team has worked on numerous externally funded projects over the past decade. Here, Maureen Pennock looks back at the work of the JISC-funded SPRUCE project, a collaborative initiative between the British Library, the University of Leeds, the Digital Preservation Coalition, the Open Planets Foundation, and London School of Economics, to support grass-roots level digital preservation activities in institutions across the UK.

Digital preservation            Digital preservation

Of all the projects we’ve been involved with in the past, the SPRUCE project stands out for not only the number of useful outputs it delivered, but also its impact on practitioners across the UK.  SPRUCE has made a real difference to the people it supported, directly engaging with the wider community to meet their requirements with practical tools and support. Community and content owners are essential aspects of digital preservation, and SPRUCE sought engagement with content owners to deliver tools and processes that they need right now. Because that’s one of the things about digital preservation: it’s not just something that you do in the future, when your content is in a repository. It’s something that you do from the very moment you first acquire content, all the way through the lifecycle. It’s an ongoing activity. 

SPRUCE mashup participants

CC by SPRUCE-style mashup at York in September 2011

A core component of SPRUCE’s success was the use of agile events such as Mashups and Hackathons. These brought together practitioners (who contribute digital data and preservation challenges) and developers (who apply tools to solve the practitioners’ challenges). Requirements, approaches, software tools and other information gathered during the events proved invaluable in developing subsequent SPRUCE outputs. The project delivered a wealth of digital preservation tools for an enormously wide range of content types, and funded twelve more for supplementary development, including:

• Enhancements to the publicly available FITS and C3PO content characterisation tools

• A Resource Audit and Comparison Tool, ReACT

• A MediaWiki extension to enable extraction and transfer of Facebook data to MediaWiki

• Appraisal and Asssessment prototype solutions

• Tools to detect bitrot and repair it

• De-duplication solutions

• Fixity and Quality Assurance tools

• Migration solutions

In addition to these content-focused events, the project brought partners together in a booksprint to deliver the first ‘Digital Preservation Business Case Tookit’. Twelve digital preservation experts spent three days in a hotel in Manchester and brainstormed the toolkit, using their own expertise and the knowledge generated throughout the course of the project. The toolkit has been widely welcomed as one of the most useful non-technical digital preservation tools currently in circulation. Readers are encouraged to use the toolkit, hosted on the DPC wiki, whenever they need a business case for digital preservation-related funding. 

Data management              Preserving digital assets

Another project highlight is the production of COPTR, the first Community Owned digital Preservation Tool Registry. COPTR consolidates a number of pre-existing tool registries, uniting and supplementing them in a centralised database so that we no longer have to search across multiple registries before finding the tool we need. Like the business case toolkit, COPTR has been heralded by the expert community for its success and usability.

We’re sad to see the end of SPRUCE. It was a great project with a small budget but a huge impact. As the funder said, ‘SPRUCE is one of the best things we’ve done for many years’. Take a look at the website, use the toolkit and the tools, and add to the wiki if you can. The project may have ended, but the community it enabled can continue to grow if we keep working together. 

Maureen Pennock

13 December 2013

Digitisation as a preservation tool; some considerations

Digitisation projects are today more and more a common and established reality in many big and small public institutions. The expectation from the public for online access has placed great pressure on public institutions which hold collections of historical and artistic value to provide it as soon as possible. Large investment in digitisation projects has had a major impact on the work pattern of many institutions, and on the collections involved in the processes related to the digitisation workflows.

I am a book conservator currently managing the conservation studio that has been created for the British Library/Qatar Foundation Partnership programme. Phase 1 runs until December 2014 and aims to digitise and make available online 500,000 images for scholars and the general public. These images will be taken from various British Library Arabic materials and it is our duty as conservators to support the digitisation process ensuring that no damage is caused to the library items processed through the digitisation workflow.

Phase box

CC by An example of a custom-made phase box for this heavily damaged manuscript

I want to present in this post some considerations about what conservation could potentially gain from these types of projects and how I think the long term preservation of historical items and their features can be improved through mass digitisation projects. The previous sentences make quite provocative statements. It is not a secret that conservators tend to look at digitisation projects, and in general at projects involving multiple processes, with caution if not suspicion. In general conservators are often against the “mass” approach and digitisation processes are primarily focused on targets that are sometimes strained under tight deadlines and budgets. This can be an unsuitable environment for the normal conservation requirements.

Conservation means attention to detail and much of the work involves time-consuming treatments carried out by skilled professionals at their benches. These treatments are often present to help public institutions achieve their aims and fulfil their strategic priorities. Enabling access to library collections is one of the more important principles of sustainable stewardship. Conservation at the British Library has in the last few years adopted the “fit for purpose” approach. With re-treatability and minimal intervention approaches clearly in mind, we know that today we have to plan our work in a more efficient and effective way. Planning is a fundamental step in our daily and long term work and to do so we need to know which specific goal we want to achieve.

In the present case for the British Library/Qatar Foundation Partnership programme, digital surrogates are the aim; good quality reproduction of items capable of providing online customers (scholars, readers and the general public) with the information they require. There are many steps between the shelves of the British Library storage areas and the cameras in the photographic studio. Conservators need to be present throughout each stage of this flow to support and to enable successful digitisation.

This can be difficult to achieve as full time conservators are expensive. Work needs to be customised but this certainly doesn’t mean compromising on the quality of the work carried out on collection items. In the context of the British Library/Qatar Foundation Partnership programme, a document about policies and procedures was produced by the conservation studio at the very beginning of the project. In this document we state that due to the scope and the nature of the project, we cannot treat items that are in need of conservation work that would take more than five hours. This means that generally we are not “fully” repairing the items we are processing through the workflow, but instead we are treating the items to a condition that enables digitisation.

After assessing the condition of the items brought into the project we decide if they are fit for handling, and if so they can proceed along the work flow. Quite often items with minor damage can still be digitised because the imaging and cataloguing processes (even if very intense from a handling point of view) are carried out in a highly monitored environment where we provide training for each member involved in handling library items, and constant support where needed.

We have also devised a colour “traffic” light system that we use to communicate through our tracking system on an online shared drive with the other strands of the project. A colour orange dot, for example, placed next to other information on the shared drive highlights that an item is in need of careful handling due to its fragile or damaged state.

SharePoint

CC by Screenshot of the SharePoint window with information about items processed. Coloured dots highlight the conservation status of these items: orange: in need of careful handling/support from conservation, green: fit for handling

By doing this we ensure that all risks relating to possible damage occurring to items during handling and use are mitigated. At the same time we make possible the creation of surrogates from items that would otherwise not be available to readers in the reading rooms due to their condition, if not only after extensive conservation work. By providing surrogates to readers we should be able to preserve the original physical item from further handling, and this can only be achieved if an item’s access is subsequently reduced.

This is already quite an achievement - when it works, but even in such a customised capacity we can do more than that and the magic word here is “housing”. Good functional housing can be provided by creating customised, and not necessarily expensive, enclosures. If correctly used, phase boxes, folders, and Melinex enclosures provide very effective solutions to prolong the existence of fragile and endangered items.

We also provide supportive treatments such as repairs to major tears and weak areas. These are carried out only to minimise the risk of further damage during handling. This does not mean that as conservators we are sacrificing our knowledge and experience, but it means that we are shifting our expertise towards a wider and more comprehensive approach regarding what we can do for the preservation of our collection.

Conservation, as the word itself says, is the profession aimed to “conserve” items and all their historical features. Looking at the few examples below it is very clear that quite often full treatments have resulted in the complete transformation of the physical nature of the treated item. New sewing, heavy repairs applied to the supports, and new arrangements of items (loose leaves to a bound format) have completely jeopardised the understanding of the physical history of those items.

Restoration

CC by Two originally “similar” items have, after restoration, lost most of their original physical appearance and therefore invaluable information related to their history

I love books and I love the feeling of handling items that are as they were meant to appear when they were produced. Physical features are an integral part of the history of an object, and too often paper based items are considered only for their content.

Nothing of importance!

CC by Unfortunately, many bindings and other physical features have been discarded as “Nothing of importance”!

In the following image it is possible to see how good intentions translated into over-restoration. This practice has caused a lot of losses of original features and therefore vital information about the item.

Guard book

CC by Guard book of documents that were originally bound together. The paper is laminated and then “hooked” with paper hinges to be bound in the present format

It gives great personal and professional satisfaction to see my input valued and to enable others to enjoy items I am conserving in their original state. It is not always possible or even advisable to completely stop to do full treatments to damaged items, but it is important to remember that we take on a great responsibility by doing it. It is a natural and understandable expectation that we want to see things “as new”, but that is not the aim of conservation.

I like to say that conservation is not about preserving what we can see, but is to be able to leave things as they are as much as possible; it is what we cannot see that really matters.

Heavily damaged manuscript
CC by This heavily damaged manuscript has been digitised and re-housed in a box. By doing this we have been able to preserve all the original features of its contemporary binding, remnants of the sewing threads and materials used in the making of the cover. These details provide clues about specific crafts employed, as well as shedding new light on issues like provenance of the object. They may even inspire new approaches for the interpretation of its content

Mass processing workflows such as those employed in digitisation projects offer conservators a great opportunity to gain understanding about entire collections and not just about single items. By processing a great number of items the conservator acquires knowledge of a whole group of items leading to a wider understanding of the collections and the issues relating to them.

It is a great challenge for conservators to make the best use of this newly acquired knowledge. We have to be able to share what we learn with other strands of our institutions, and also more broadly with interested outside audiences. Information dissemination has never been easier with blogs and Twitter feeds allowing us to share our knowledge quickly and efficiently. It is an opportunity for better communication that we should embrace.

Flavio Marzo

Gulf History Arabic Science Project Conservator

02 December 2013

Read All About It #1 - What’s in the Papers?

“Life is a series of hellos and goodbyes, I’m afraid it’s time for goodbye again, Say goodbye to Colindale. Say goodbye, my baby…” [with apologies to Billy Joel]

The oldest newspaper

So. The Newspaper Library at Colindale finally closed its doors to the public on 8 November this year, having first opened them to readers more than eighty years ago. Like many of you, we’ll miss the old place for all sorts of personal reasons – for the things we discovered there, the friends we made there, the experiences we shared there.

But professionally, being charged with preserving its vast collection and keeping it available, we can’t be too sad, because we know that, by closing its old doors, we are opening a new one and taking a massive, exciting step towards a better, more stable future for the collection and a much improved experience for those who want to use it.

Reading Room at Colindale 1970

CC by The reading room at Colindale, c. 1970                                                   

The sun’ll come out, tomorrow…

The Colindale building opened in 1905 for the storage of newspapers, which means today that we have a double collection care whammy – a very vulnerable collection (let’s face it, newspapers were never meant to be kept for hundreds of years) stored in a very inappropriate building. The main enemies of organic material – light, temperature, humidity and particulates – were unable to be controlled as efficiently and cost effectively as we needed to at Colindale to ensure the future of the collection. This unsuitable and unstable environment was catalysing the natural deterioration process of the organic materials that make up the collection, which means we need to take urgent action.

Sunshine at Colindale

CC by Sunlight falls on the Colindale collection

For example, there are over 450 windows in the stacks at Colindale – one at each end of every range – which has allows sunlight to do its damage visually and chemically over the years. Sometimes open and sometimes closed variously across the six floors of storage, they also make the temperature and humidity difficult to control and the fluctuations in these in particular are contributing to the condition of the collection.  Solar gain is augmented by old radiators in between every second window, part of an original heating system that can’t be controlled centrally or sensitively.

Shelving at Colindale

CC by Sunlight falling on the shelves at Colindale in North London

Newsprint

What’s in the papers?

For our readers and users, what’s in the papers is what it’s all about. The content of our Newspaper Collection is a rich and vibrant source of information that draws researchers from all over the world. But for those of us whose job it is to care for the collection and keep it available, what’s literally in them (what they’re made of), is more important, because it has a significant impact on their life expectancy and our management of it.

Getting enough of the right fibre

Newspaper is made from cellulose fibres and up until the mid/late 19th century, the most common source for this was recycled textiles, or rags (largely, but not exclusively, from cotton and linen). Rag papers have lovely long, strong fibres of pure cellulose and, although all cellulose-based papers produce acid-based by-products through natural degradation, kept in the right environment (more of that later), and handled appropriately (more of that, too), they will stand up naturally well to the challenges of time and use.

But cotton and linen rag was not a sustainable source for newsprint, and a shortage of rags combined with an increased demand for paper led to development and use of wood as the primary source of paper pulp – and inadvertently presented us with a major preservation headache… 

Wood pulpWood

The problem that wood pulp papers give us is that wood contains lignin (amongst other things), a complex polymer that binds the cellulose fibres into a cohesive structure. And the trouble with lignin is that it’s light sensitive. It will degrade and discolour on exposure to light, weakening any paper that contains it.

If you leave a newspaper in the sun for just a few days you’ll see the start of this degradation process by the discolouration of the exposed pages. Leave it longer and the pages will become brittle and will physically break when handled.

Wood and rag fibre comparison

CC by Wood fibres (here on the left) provide a weaker bonding matrix than rag fibres

Brittle newspaper can be virtually unmanageable. If you’ve ever requested a newspaper item and have been advised that it is not able to be issued for preservation reasons, frequently (but not always) it will be because the item is too vulnerable to loss of content and further damage as a result of brittle paper:

Brittle paper

CC by These volumes of regional papers from 1908 show the effect of brittle paper. Sometime brittle paper affects only certain areas of the page (often the outer edges) and only parts of a volume, but some are brittle throughout and their weakened pages detach readily. Handling is difficult and loss of content inevitable. Neither of these volumes would be available for issue under normal circumstances

When you realise that of the approximately 282,000 bound volumes of newspapers currently at Colindale, over 90% are published after 1850 and fall into that window where rag pulp was starting to be superseded by wood pulp, you get an idea of the scale of the challenge we face in trying to preserve the collection and keep it available.

Stopping the rot

Another challenge we face is 'red rot'. Atmospheric sulphur dioxide absorbed into leather bindings over many years oxides to form sulphuric acid which dissolves the leather to red powdery material of no physical strength. While leather degradation by red rot can’t be reversed, the rate can be slowed by improving the environmental conditions in which volumes are stored and reducing their exposure to natural light.

Scottish papers  Scottish papers quarter bound
CC by These volumes of Scottish papers were originally quarter bound in blue leather, but the leather on the spines where the spines are exposed to the atmosphere, has been seriously degraded by red rot

Degraded leather on spine 

CC by We can see that the leather on the spine has completely degraded away, exposing the spine lining which was glued up using a hot-melt glue. The kettle stitch and cords are exposed and continued use will result in this volume completely disbinding

Size Matters

Brittle paper and red rot are common conditions that we have to dea l with, but these are often compounded by the size of many of the items in the collection.

“…and my pocket sonnets are yours, Miss Marianne!”  Thus Mr Willoughby confirmed the gift of his teensy little bound volume of Shakespeare sonnets to Marianne Dashwood in the film version of Sense and Sensibility.

Imagine the alternative newspaper version:

“…and my bound volume of the Argus, Clarion and Trumpet Jan-Dec is yours, Miss Marianne! You fellows bring her on up! Steady...Curses, mind the lintels! This bookcase shall have to be rebuilt to accommodate her. And the reading table much extended and reinforced…she’s of monstrous size (no, no, not you My Love…!)"

The Birmingham Stock Exchange Monthly Investment List 

CC by Left: This is one of our smallest volumes, the Birmingham Stock Exchange Monthly Investment List. The volume here is dated 1910 and, no taller than a pencil, measures 14cm x 8.5cm and weighs only 100g

Binding newspapers into volumes was a practical way of keeping them together and protecting the pages from physical damage as well as, to some degree, harmful light and particulates. But this means that we have many items in the collection that are of significant size and weight, which makes handing very difficult. This can lead to physical damage of stable material and significant damage to unstable material.

By contrast, this volume of the Alloa Journal & Clackmannanshire advertiser 1895 [left-most volume below], while still not the largest volume in the collection, measures 82.5cm x 61cm and weighs in at an impressive 17.51 kg.

Damage to text block

CC by In the example above the text block, over time and with use, has dropped out of its binding under its own weight. With both boards detached the text block is no longer properly protected. It is not only suffering damage but is increasingly difficult to handle.

Next post: Paper, paper everywhere, and not a page to read…

We know our newspaper collection is a brilliant resource for many different people for all sorts of reasons, and it’s crucial to us that we continue to make as much of it available as possible. In our next post, Building a Future, we’ll look at the steps we’ve taken over the years to provide content where originals are too fragile, including conservation, microfilming and digitisation; the effect on the collection of the current building and the preservation justification for moving; and we’ll look inside the new building and explore its benefits and advantages.

For more information on the newspaper moves programme see our Newspaper Moves web page.

Sandy Ryan