August 2018 - Digitization is like playing darts...

.... only with precision, accuracy and stability you will hit the bullseye regularly


Time and again, libraries are challenged in their digitization activities to create digital copies that contain all the content and information of the original. Valuable help with this task is provided by the Metamorfoze guidelines for image quality. We talked to the "father" of the directive, Hans van Dormolen about their importance and content and what Metamorfoze has to do with playing darts.

At a young age, Hans van Dormolen developed a passion for photography, aroused by his father, who worked as a journalist and photographer. Since then, the fascination with the magic of the Camera Obscura has been preserved.

After studying photography, he worked from 1985 to 2000 as a freelance photographer. He then took a job as a photographer at the Dutch National Library (Koninklijke Bibliotheek / KB), but a short time later he carried out research for the library. He is the founder of Hans van Dormolen Imaging & Preservation Imaging (HIP) and since 2012 he is working as an independend imaging consultant worldwide. 

What is the background of Metamorfoze?
Hans van Dormolen: Metamorfoze is the national program of the Netherlands for the preservation of the paper-based cultural heritage. The program is implemented by an independent "Office Metamorfoze", which is located in the Dutch National Library. Whereas in the past it was mainly microfilmed, today mass digitization projects are in focus. However, in order to continuously achieve a high image quality, clear guidelines are required that can be objectively verified. These specifications are clearly defined and described in the Metamorfoze guidelines.

And how did you take a leading role in the development of the guidelines?
As part of my research work at the National Library in 2001, I was commissioned to develop guidelines for preservation microfilming. During this time I learned a lot about the technical basics for good and reliable reproductions. These insights then flowed into the Metamorfoze guidelines for the digitization of two-dimensional materials. These include books, manuscripts, magazines and newspapers, but also photographs, paintings and technical drawings.

A total of 7 years - from 2005 to 2012 - Hans van Dormolen worked on the "Metamorfoze Preservation Imaging Guidelines". Many cultural institutions on a national level, such as the National Archives of the Netherlands, the Rijksmuseum Amsterdam and the Van Gogh Museum, but also international institutions such as the Metropolitan Museum of Art, supported him in his work. He also benefited from close collaboration with scanner and camera manufacturers, including Zeutschel and Leaf. After various concepts, the first official version 1.0 was released in January 2012. It is freely available on the Internet:

What is the goal of the Metamorfoze Guidelines?
Hans van Dormolen: The goal of the Metamorfoze guidelines is very simple: All visible information in the original must also be visible in the digital image. For this purpose, so-called "Preservation Masters" are to be created, which are of such a quality that they can replace the original. In this way also the protection of the originals is contributed, which - once digitized - will be used in the future only in exceptional cases. The master files can then be used to create derivatives for a wide range of applications, for example for publication on the Internet.

You often compare digitization with playing darts and define the Metamorfoze guidelines as an instruction, in order to always “hit the bullseye”. What do you mean by that?
If you want to be successful in darts, you need three key features: precision, accuracy and stability. The latter ensures that a direct hit or a so-intended throw was not coincidence or a fluke, but can be repeated regularly. The same thing - precision, accuracy and stability - also applies to Metamorfoze digitization. The criteria and tolerances described in the guidelines ensure a consistently high image quality on a regular basis, day after day.

Which technical criteria are particularly important for a high image quality?
Hans van Dormolen: The most important aspect and the foundation of the Metamorfoze guidelines is the correct tonal capture. This is the USP of Metamorfoze compared to the other standards and guidelines.

At this point of the conversation there is a short break. The journalist looks a bit disbelieving and surprised. Hans van Dormolen smiles. He knows what he's talking about. When he analyzed the quality of old microfilms produced in the Dutch National Library in 1960, ’70,’80 and ‘90, he was shocked to discover that although the microfilms had excellent resolution, the tonal capture was always very poor. The result: As a rule, only 1/12 of the original can be seen on the microfilm copy. In other words, 11/12 of the original's tonal information was lost in the microfilming process.

How can the tonal capture be done correctly?
Correct tonal capture starts with: correct white balance, correct exposure and correct gain modulation. Correct gain modulation ensures that all the visible information of the original is also visible in the digital image in exactly the same way. That really means that “what you see is what you get”. And this also means that no visual information of the original is lost!

The Metamorfoze guidelines provide for three quality levels. What are the differences?
Hans van Dormolen: All three quality levels ensure correct tonal capture. And all of them are applicable for small and big digitization projects.
The quality level "Metamorfoze" is designed for th digitization of originals that can be seen as works of art, for example manuscripts like the letters of Vincent van Gogh, photo collections, maps and paintings. At this highest quality level, in addition to correct tone capture, high color accuracy is also mandatory. This means that the colors in the digital reproduction correspond as close as possible to the original.

Digitizing after "Metamorfoze Light" requires good color accuracy. Typical materials are manuscripts, magazines, books and newspapers. For the two mentioned quality levels, the use of technical test charts in every image is compulsory.

At the third quality level "Metamorfoze Extra Light", the use of technical test charts in every image is optional.  This quality level can be used to digitize books, newspapers and magazines.

The Metamorfoze guidelines contain the technical criteria and the corresponding reference values for a high image quality. To apply them successfully in practice, there are tools available. Among these, the so-called "Universal Test Target (UTT)" plays an important role. It provides the user with all the information needed to determine if an image meets the required image quality standards and guidelines. In conjunction with scan systems that meet the quality levels of the guidelines and evaluation software, quality control can be highly automated.

The test chart was developed jointly by The Dutch National Library / Hans van Dormolen as well as the companies Image Engineering Dietmar Wueller and Zeutschel on behalf of the “Fachverband für Multimediale Informationsverarbeitung (FMI) e.V.“ 

From the UTT testing process and the content of existing international guidelines - such as Metamorfoze and the FADGI initiative known in the US – emerged the ISO standard 19264-1, published in 2017. The second part of the interview informs you about these topics and developments.

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