Technical Advisory Service
2001 - 2004 archive
Frequently Asked Questions
The questions and answers on this page have been asked by nof-digitise applicants. This page will be updated frequently.
1. What are suitable methods for storing electronic photos?
Image management systems can be used for a wide range of purposes, including: managing workflows, storing metadata, maintaining relationships between images and their metadata, user access, etc., so you need to have a clear idea of what you would want from an image management system (e.g. some functional requirements), in order to decide whether the current library system would be able to do the job properly.
In general, many library systems have now started to have
image management capabilities, but it is sometimes difficult to
know how well it has been implemented. The vendor's information
on DB/TextWorks at:
Some general advice on database management systems has been
produced by TASI:
Peter Hirtle also has a chapter on image management systems in Kenney and Reiger's book "Theory into practice" (RLG, 2000).
2. Can you advise if backup onto CD of digital resources is sufficient for preservation purposes.
Copying to CD might be useful for short term backups but that on its own it isn't a very sustainable *long-term* preservation strategy. The reason for this is that the dyes used by recordable CDs (CD-R) tend to break down over time.
For more information, see section: 1.1.6 in Ross and Gow
(1999). The same authors wrote in their executive summary that
they felt that the stability of CD-R was over-rated and "far from
being a secure medium it is unstable and prone to degradation
under all but the best storage conditions." Best practice would
beto keep an additional copy on some magnetic media. For more
details see: Ross, S., Gow, A., 1999, Digital archaeology:
rescuing neglected and damaged data resources. London: South Bank
University, Library Information Technology Centre,
In practice, preservation is about managing information content over time. It is not enough just to make backups, but to create (at the time of digitisation) well-documented digital master files. Copies of these files should be stored on more than one media type, and (ideally) in more than one geographical location. These files should be used to derive other files used for user access (which may be in different formats) and would be the versions used for later format migration or for the repackaging of information content. If the files are images, the 'master' file format should be uncompressed, e.g. something like TIFF.
This is not to denigrate making backups in any way. Any service will need to generate these to facilitate its recovery in the case of disaster.
Creating a full 'digital master' with associated metadata will be a complex (and therefore expensive) task that should be done once only and at the time that the resource is being digitised. All equipment needs (or the choice of a digitisation bureau) should be considered with the creation of such digital masters in mind.
Projects will also need to decide where these digital masters should be kept for the duration of the project itself and where backup copies of them (and maybe other parts of the service) should be stored. Thought could be given to subscribing to a third-party storage service. An example is the National Data Repository at the University of London Computer Center (ULCC). More information on the services offered by the National Data Repository Service is available at:
The various service providers of the Arts and Humanities Data Service (AHDS) will also provide a long-term storage service for digital resources. They have also published various guides to good practice. For more information, see:
3. Can you clarify the emphisis that NOF is placing on digital preservation?
The nof-digitise programme is linked to lifelong learning and the overriding objective is to fund the digitisation of a wide range of materials that will be available free of charge at the point of access on the People's Network and National Grid for Learning.
It is important to secure the long-term future of materials created, so that the benefit of the investment is maximised and the cultural record is maintained in its historical continuity and media diversity. Therefore preservation issues should be considered an integral part of the digital creation process.
Projects should consider the value in creating a fully documented high-quality digital master from which all other versions (e.g. compressed versions for accessing via the Web) can be derived. This will help with the periodic migration of data and with the development of new products and resources.
NOF is providing guidance to applicants on digital preservation, further details of which can be found in the nof-digitise Technical Standards and Guidelines.
Have a look at the TASI site. They have a fair amount of information on Data Capture and Creation - http://www.tasi.ac.uk/advice/creating/creating.html.
However questions regarding your awkward objects are best answered by a good professional photographer. Photography of strange 3d objects will need all the skills of a photographer, and really it does not make any difference if the images are being shot with a digital camera or a film one. The main problems are those of lighting and photo-craft rather than anything to do with 'digital' imaging. Photoskills at that level are hard to teach and hard to provide any material for on a Web site, really it just comes down to experience, as different things will need different lighting setups and backgrounds. Standardisation of lighting and background will make the images far easier to present and work with once they are part of a collection.
5. Is it really necessary to digitally watermark our images as those we are making available for the web are compartively low quality and we would freely allow their use for non-profit, educational uses anyway?
The NOF Technical standards states on the matter of watermarking and fingerprinting that "Projects should give consideration to watermarking and fingerprinting the digital material they produce." Must has not been used therefore it is up to individual projects if they want to use this method of copyrighting.
If your project aims to make your resources available for non-profit, educational use, your online images will be of comparatively low quality and you have a copyright statement on your site then watermarking will probably not be necessary for your images. If you feel that your money could be used more constructively in another way then you are free to do this. Note that it may be worth making a note of this choice and the reasons why you have done it and add it to your Project Plan for future reference for your case manager.
For alternatives to Digimark have a look at this page on the TASI Web site: http://www.tasi.ac.uk/advice/using/uissues.html
You may also find the information about Copyright, IPR, Ethics and Data Protection useful: http://www.tasi.ac.uk/advice/managing/copyright.html.
First, Archival and preservation are both just words....they are not standards and do not have any exact values.
second, what is archival or preservation for one project or image will not necessarily be so for another. This totally depends on what the intended use of the image is. It would be the intention to archive or preserve all the quality that is required to present the image to the highest quality chosen as appropriate for delivery. This of course sounds like a chicken or egg situation and for any project, the first question is to decide what level of quality is appropriate for that image.
There are very many ways of going about making this decision....
You could decide on a largest output printed size required for images, for instance A3 quality print would mean 50Mb or so, A4print would mean about 24Mb. If like the National Gallery you wish to create life size copies, then you would need many hundred Mb for each image.
You could decide on how much visual information is kept within the image and then choose appropriately. For instance a 20ft x 12ft painting is going to have more visual information in it than a postage stamp, but also a turner watercolour will have much less visual information in it that a Turner engraving. The watercolour will be visually interesting with acceptable quality to understand and appreciate the image with about 800 x 600 pix but the engraving would be meaningless at this resolution and would need to be imaged at 3000 x 2000 (at least) to show the vast amount of visual information contained within the image.
Of course this is also dependent upon who the user is. A teacher wanting to show a Turner watercolour wants to show the whole image on screen to her students......the paper historian wants to zoom right into the image to be able to see the paper detail. Both are legitimate but a decision has to be made as to what level of detail the project wishes to capture.
As a rule of thumb, to print an image at the same size as the original you need approx 300ppi for a continuous tone image and 600ppi for a bi-tonal image. It is these figures that are sometimes erroneously given as 'preservation' and 'archive' quality......but don't just grab these figures and stop thinking about the more fundamental issues.
There are different influences as well......Do you wish to have a standard image quality within your collection (advisable normally!) so they are all the same size. This makes it much easier to work with as you always know how big every image is....because they are the same. On the other hand if you had a collection of maps and stamps, then what was right for one would be totally inappropriate for the other and you would need to at least have two standards...
But the key to this, is that you have to decide or research:
How much visual information within the image needs to be captured
Having found those out, you can decide what size the captured image needs to be to fulfill your requirements......When you know what you need....it is easy enough to find out what the appropriate resolution is to give you that.
Having done that.....it is simple.....you just preserve and archive a file that is big enough to provide you with all the quality that fulfills your needs.
For further information see http://www.tasi.ac.uk/advice/creating/digitalimage.html
And what is the recommended capture resolution/file size for archived material?
We don't recommend absolute file sizes because they depend upon a host of factors, including physical image size, scan resolution, file format, and colour depth. There are just too many variables to enunciate sensibly in something like the Technical Standards and Guidelines document.
Instead, you should bear in mind the need for preservation, re-use, etc, and should scan as well as feasible, using your judgment and working conditions.
"Images should be 8Mb" is a totally useless statement in itself.
It is true that capture resolution is linked to scale. We would assume 1:1 for the scale in most cases, except where that wasn't feasible.
There is some very useful information on exactly this problem at the TASI Web site: http://www.tasi.ac.uk/advice/creating/creating.html. The TASI Web site gives useful information on the decision making process. Another source that provides useful information is the AHDS Visual Arts Data Service Guide to Good Practice for creators of visual resources. The Guide can be found at: http://vads.ahds.ac.uk and look under Guides to Good Practice.
Some points to bear in mind when going for archival quality:
1) The better equipment for taking a digital copy of a sheet of paper is a scanner. A camera will distort the geometry of the page around the edges - perhaps not enough to be visible, but still it remains a fact of life of capturing an image through a glass lens.
2) Use of a camera would have to be controlled: I would not recommend that the camera was held by hand, it should be mounted on a support of some kind, and lighting conditions would have to be suitable.
3) Use of a camera may be appropriate if the nature of the material is delicate and subject to damage on a flatbed scanner.
4) The key parameters for judging the file size are:
5) With regard to the filesizes, TIFF is a suitable format for preservation. The difference in file size is probably because one is stored uncompressed and the other is probably compressed with the LZW algorithm. From a long term perspective use of LZW is not recommended as the algorithm used is patented (same codec as used in GIF), and there may be cost implications down the line. There are other compression schemes available for TIFF, and storing the collection of TIFF files in a compressed archive may also be effective (ie zip, tar, rar etc)
6) With regard to filesizes, the other issue is the colour depth (bit depth) - ie the number of bits used to store colour information. This is generally 24 bit (ie 8 bit per RGB channel).
In conclusion I would recommend that you look carefully at the digitisation process and the results. Once you are satisfied that you have chosen the superior method of digitisation, then worry about the file storage problems.
8. A small museum has found during a trial of digitising its 5X8
b/w glass negatives at 600dpi and saving in TIFF files, that
this level of resolution places far too great a demand on the
museum in terms system resources and processing time - files are
being saved at up to 235MB and can take a long time to open. The
guidance given by the NOF standards and other HE advisory
agencies recommends scanning to 'best resolution within an
organisation's budget and resources'.
There is always a compromise between the quality that would be needed to use the image file for conservation and the cost of digitisation and storage of that file. Where that compromise is made is dependant upon the resources of the organisation.
There is no magic figure that can be given as a correct resolution as this will always depend upon the size of the item that is being digitised and its intended use.
That is why the recommendations state that scanning should be to 'best resolution within a organisation's budget and resources'.
For an organisation to work out what they can and cannot afford they must start at the other end of the workflow by establishing what is the organisations budget and resources. From that, they can establish what file size they can create within that budget.
The budget will control the amount of storage space available to the project. You can divide the available space by the number of items and get a maximum file-size possible within the 'budget and resources'.
Whether the file size that you have created will be big enough will depend on what it is that you want to do with it. We would suggest that 235Mb is certainly a very large file and could produce beautiful large prints but is most probably more than you need to produce for most digitisation projects.
If the goal of the project was to solely produce images to be used via a monitor delivery system then these images would indeed be quite vast!
As a rough rule of thumb we would recommend that you worked to something like these guidelines:
Create files big enough to produce A4 b/w printed images at 300lpi:
this would need b/w files of approx 8.25Mb (A4 8bit b/w at 300ppi)
If your intention was to produce colour files, they would look nicer, then they would need to be 24.8Mb (A4 24bit col at 300ppi)
(Other possibilities would be to save the file in 16bit b/w which would certainly be better quality but giving larger files. Or the image could be digitised at a size big enough to create bigger output sizes, eg up to A3?)
Continuing on this basis, the 5x8 inch negatives would need to be scanned at 450ppi to create the filesize we have discussed.
This however is much smaller than the 235Mb that they are
They are scanning at a much higher res than 600ppi. The are scanning at a very high colour depth like 48bit colour.
If space and money are an issue then we would question whether this is the best way forward.
We have to still point out that there is no magic "correct res" as it is totally dependent upon the size of the original and intended use of the images within the project.
9. The 10,000 digitised images we hope to have on our Web site will have been either photographed or scanned. However, we would also like to include a small amount of slides of historic costume that we believe it would be detrimental to handle again in order for them to be re-photographed. Having examined the slides, they are not as good a quality as we are now capturing, and although they will look fine on the web they they will not make for good archival images. Is it possible for us to use these slides, or should we not include them and therefore leave out some important historical costume items that we would very much like to include?
It sounds like you have a fairly common problem on your hands - deciding what to digitise is never easy. You may have tried using the matrix approach already in selecting, if not some of these sites may be of interest:
The best matrix I've seen is in Stuart Lee's book 'Digital Imaging: a practical handbook' Lee does say that there isn't weighting attached to categories nor is it suggested that you just add up the number of ticks under each section and give items a score. The matrix is more for demonstrating that you've taken the selection criteria serious and have made some analysis.
With the slides you talk about you really will just have to weigh up the pros (their important historical value) and cons (scanning slides may take longer and as you've explained the quality isn't that good - no archival master) of using them and decide what is the most important.
NOF-digitise would accept the use of these slides because there is significant historical value attached and they will be very useful for learning (and that is what the programme is all about). Also the number of slides to be used only makes up a small number or your overall collection. However I would advise adding something to your quarterly progress report about your intentions and mentioning them to your case manager.
You might also find the section on creating digital images from slides on the TASI site useful as you will need to optimise their quality.
1. Is there a definitive guide available about developing government and UfI standards?
See http://www.govtalk.gov.uk/ and http://www.iagchampions.gov.uk/ for more information on e-Government and the Interoperability Framework and http://www.ufiltd.co.uk/materials/qualified.htm for UfI standards documents.
Also, Paul Miller provides an overview of Government Web stanadards in his presetation to the Public Library Web Managers Workshop, available at: http://www.ukoln.ac.uk/public/events/managing/miller/
2. Is there any general information or guidelines about how to choose the right web hosting company, ie what we should be looking for, what kind of questions should we ask a potential supplier...?
Questions to ask of potential suppliers are:
Backup arrangements - How will they back-up your data? How often? How quickly can you get it back?
Hardware support arrangements - What will they do when the disk that your data is on breaks? Do they run RAID of any kind. How long to replace the disk and get back data (see above).
Security policies - How do they make their systems secure? What facilities do they offer to other users of the same machine.
Available bandwidth - What kind of connectivity do they have? What peak-time traffic do they have using that bandwidth?
3. What sort of bandwidth will be available for delivery of nof-digi projects?
Up to 20% of schools (mainly secondary) will be connected at 2mbps by end of 2002, the rest will be ISDN2. Libraries have an aspiration for all public libraries to be connected at 2Mbps by end of 2002. But do remember, though, the needs of home users, who may well be using traditional modems. They don't necessarily need full functionality, but they do need to be catered for.
4. Could you explain what is meant by 'Web services' in para 3 of Section 5.1.1: Access to Resources, i.e. "Web services must be accessible to a wide range of browsers and hardware devices (e.g. PDAs)..."
The term "Web service" means, in this context, Web site.
The resources which are being digitised through the NOF digitisation programme are expected to be available for a long period and to be accessible to new devices which may be developed in the future.
Even today PDAs can be used to access Web sites containing images, and in the near future we can expect PDAs to have multimedia capabilities. We are also hearing the term E-Book Library being used instead of E-Book Reader to convey a future in which large amounts of data can be stored on mobile devices.
In order to ensure that NOF projects can exploit such devices they should be based on open standards (such as XML) as opposed to using formats which are aimed at desktop devices.
5. What is meant by open (as opposed to proprietary) standards? How does a standard become a standard? Are there standards awarding bodies?
Proprietary file formats (such as the Microsoft Word format, Abobe PDF, Macromedia Flash, etc.) are owned by a company or organisation. The company is at liberties to make changes to the format or to change the licence conditions governing use of the format (including software to create files and software to view files). Use of proprietary formats leaves the user hostage to fortune - for example the owner of a popular and widely-used format may increase the costs of its software (or introduce charges for viewing software).
Open formats are not owned by a copany or organisation - instead they are owned by a national or international body which is indendent of individual companies.
Many standards bodies exist. Within the Web community important standards organisations include the World Wide Web Consortium (W3C), the Internet Engineering Task Force (IETF), ECMA (European Computer Manufactures Association), ISO, etc. These standards organisations have different cultures and working practices and coverage. W3C, for example, is a consortium of member organisations (who pay $5,000 to $50,000 per year to be members). W3C seeks to develop concensus amongst its members on the development of core Web standards. The IETF, in contrast with the W3C, is open to individuals. ISO probably has the most bureaucratic structure, but can develop robust standards. The bodies have different approaches to defining standards - ISO, for example, solicits comments from member organisations (national standards bodies) whereas W3C solicits comments from member organisations and from the general public.
Further information can be obtained from the following Web sites:
W3C - http://www.w3c.org/
IETF - http://www.ietf.org/
ISO - http://www.iso.ch/
ECMA - http://www.ecma.ch/
NISO - www.niso.org
IEEE - www.ieee.org
IMS - www.imsproject.org
The following resources have further links to standards bodies:
An overview of Web standards is available at:
You should not confuse "open standards" with "open source". Open source software means that the source code of the software is available for you to modify and the software is available for free. This is in contrast to licensed (or proprietary) software in which the source of the software is not normally available. Both open source and proprietary software can be used to create and view open standard formats.
6. Does our web service have to be available 24 hours a day, 7 days a week?
The Technical Standards have recently changes their wording on this area. They now state "Projects should seek to provide maximum availability of their project Web site. Significant periods of unavailability should be brought to the attention of the NOF case manager and in addition should be reported to NOF through the standard quarterly reporting process. "
Projects should aim for as high level of availability as is possible. However, 24/7 cover is likely to be quite expensive and the cost/benefit doesn't justify it. Ensuring that you can ensure a fast response to breakdowns during office hours is acceptable.
There is no simple answer to this question, and I am afraid that we do not have any figures that you could use to guide you. Each web resource is unique in this aspect and giving you the user figures for a different Web site would be of no use to you. Below are some pointers that might help you to come to a sensible estimate of the type of load to anticipate.
Do you have any existing web services within your organisation? What usage rates do they generate?
Do you have any usage statistics to any other institutions? Museums, Libraries, etc? These may give you a starting figure.
Do you have a feel for your target audience - perhaps you can derive a figure from the numbers of students who may use your resource?
How many users would you *like* to have?
However, in all cases these figures will leave you with but a very rough feel for what might happen, and the very nature of a web project means that usage rates depend on many things and are very unpredictable. However, it is likely that demand will build up over time as word of your site disseminates, search engines start to index pages and people start to link to your site. Monitor your site usage carefully to observe this happening. Have a look at the Web Site Performance Monitoring Information paper for advice on how to do this.
From a technical point of view you will need to establish some ballpark target figures to enable the system architecture to be specified: some of these figures would be:
From these figures the total bandwidth requirements can be calculated. Web hosts often will cap the monthly bandwidth available to you, so it is good to have a feel for this.
You also need to consider what is the maximum number of connections you will have to your web server at one time. This can impact on the system performance in many ways...The maximum number of simultaneous users will help you establish the maximum network throughput you will require: This too is usually restricted at a web host, so that you will be restricted to a data rate of say 128 kbps.
However, that said, it is our experience that the average hosting deal, of say 15GB per month data transfer and a network connection of 128 kbps, connected to a bog standard spec PC (say 1Ghz / 256 MB RAM) will host a healthy busy website - say maximum 50 simultaneous users and 10,000 page requests per day...
Whilst we would definitely recommend that you consider this issue and derive some target figures that you expect to achieve (this is a way for you to measure the success of your site as much as anything else), we would suggest that you work with your 3rd party suppliers to achieve this as they should be able to offer some good real-world experience of usage and help guide you in creating a system architecture.
NOF-digi projects can advertise positions on the NOF-digi list - for information on how to join see http://www.jiscmail.ac.uk/lists/NOF-DIGI.html. There is also a job bank where you can advertise NOF-digitise vacancies on the People's Network site: http://www.peoplesnetwork.gov.uk/content/jobbank.asp.
Also the following Web sites may be useful:
Print journals you could try include the CLIP (what was the Library Association) jobs pullout (http://www.cilip.org.uk/) they also run Lisjobnet online and INFOMatch. There's also the Guardian.
I would also have a look at the section on human resources available in the programme manual: http://www.ukoln.ac.uk/nof/support/manual/human-resources/
Knowing how to write for the Web is an important area of accessibility. NOF believe that it is very important that sites are written in plain English for people with learning difficulties. It is felt that beneficiaries of funds should have to commit themselves to this, as well as providing a level of content accessibility. There is also a need for research to bring together existing and emerging good practice and develop tailor made guidance and this is something NOF is working on.
Listed below are some relevant Web sites that you might find useful:
Writing for the Web - Jakob Nielson
Accessible web design
Writing for the Web
Web site tips
Funding streams are changing all the time so you need to keep your ear to the ground and watch out for messages to mailing lists and articles in magazines.
Some of the possible main funding streams/bodies are listed below:
UK Funding Streams
European Funding Streams
Worldwide/Global Funding Streams
A useful document titled 'Overview of funding streams for libraries and learning in England report' is available from Resource:
This page also has some useful links http://www.ceangal.com/diglibs/funding.html
An example of good practice in handling 'Issues' and documenting how they are being dealt with has been provided by the Cistercians in Yorkshire project. They create word documents detailing each issue and how it is resolved. Such information could be held in a content management system.
1. All projects are expected to have at least some live content publicly available on a Web site by 31 December 2002.
2. From the point at which your Web site goes live you are expected to start recording a) Web usage statistics (see point 5. Below) and b) responses from users through a user feedback form on your site. User forms should be prominently displayed or signposted from your home page. The Fund is not specifying the questions to be asked on the form, as this will vary depending on the information individual projects may want to collect to meet their own user evaluation targets. It would be helpful however for projects within each consortium to discuss and share views on the design of the forms, particularly where projects have had prior experience of evaluating online user involvement. We would encourage you to share your proposals widely with other nof-digi projects through the programme email list email@example.com and the NOF-DIGI@jiscmail.ac.uk list.
3. Before the end of December 2002 the Fund will email you a form for the Annual Monitoring Report (AMR) which will contain questions related to the above information. The first AMR for each project is required to be completed and returned to NOF by 31 December 2003 (unless you have been requested to return the form earlier by your Case Manager).
4. To ensure that we are able to collect sufficient data and to certify that sites are operational throughout the monitoring period, the Fund will require at least three AMRs from each project, depending on when the content will be completed. Some of the longer projects may be expected to submit up to five AMRs. Your case manager will confirm the next due date each year when your report is requested. The Fund will also be carrying out independent checks on web site availability during the monitoring period.
5. The AMR will include (apart from standard information about your organisation and its finances) several questions about the usage of your site, which you will be able to collect through the use of Web statistics software such as Web Trends and Analog.
Further information is available here:
6. If you have any queries about how this affects your particular project please contact your designated NOF Case Manager (via the firstname.lastname@example.org email).
Defintions - taken from Web Trends
A hit - a hit is a request to the server for a file. This includes all the images, audio, graphics, pages and other supporting files as well as the HTML files themselves.
Page Views - Pages are files with the extensions htm, html, shtml, asp and so on as defined in webtrends. This value gives the number of pages viewed, not all the supporting files. This means that the total number of hits is always bigger that the number of page views. For example if a web page had five graphics files on it, everytime a user visited that page 6 successful hits would be reported, and only 1 page view.
User Sessions - A single user session is defined as a person accessing the site. If they are inactive for more than 30 minutes then a new session is started.
Visitors - This attribute is taken from the IP address or username in the logfile. An individual visitor is specified by its individual IP address of the computer being used. For example the number of Unique Visitors is the number of different IP addresses in the log file.
Further Definitions - http://www.ukoln.ac.uk/nof/support/help/papers/performance/#interpreting
Web Trends - http://www.netiq.com/webtrends/
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T A S : 2 0 0 1 - 2 0 0 4 : A R C H I V E
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