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Wednesday, 24 September 2014

To crop or not to crop? Preparing images for page turning applications

How do you prepare digital images of physical archive volumes for display within a web-based page turning application?

I thought this was going to be a fairly straight forward question when I was faced with it a couple of months ago.

Over the summer I have been supervising an internship project with the goal of finalising a set of exisiting digital images for display within a page turning application. The images were digital surrogates of the visitation records for the Archdeaconry of York between 1598 and 1690 (for more information about these records see our project page on the Borthwick website).

I soon realised that there are many ways of approaching this problem and few standard answers.

Google is normally my friend but googling the problem surfaced only guidelines geared towards particular tools and technologies - not the generic guides to good practice in this area that I was hoping for.

Page turning for digital versions of modern books is fairly straightforward. They will be uniform in size and shape, with few idiosyncrasies. The images will be cropped right down to the edges of the page resulting in a crisp and consistent presentation. 

However, we have slightly different expectations of digital surrogates of an archival volume. When photographing material from the archives it is good practice to leave a clear border around the edge of the physical document. This makes it explicit that the whole page has been captured and helps people to make a judgement on the authenticity of the digital surrogate. 


For archival volumes we have decided the best strategy is to leave a thin border around the edges of the page as shown on the left. The problem with the right image is that it is not clear that the whole page has been captured.

Volumes that we find in the archives are unique and idiosyncratic and often refuse to conform to the standard that we see in modern books. Exceptions are the norm in archives and this can make digitisation and display slightly more challenging. Page turning can work in this context, but it does require a little more thought:


Volumes within the archives do not
always have straight edges!

  • Bound volumes within the archives are not always uniform. Straight edges are rare. Damage is sometimes present, pages may even have holes in allowing other pages to be visible underneath. Should such pages be imaged as is, or should we insert a sheet underneath the page so we can see only the page that is being imaged?
  • Page size may not be consistent. A volume may contain pages of all different shapes and sizes. Fold outs may be present - meaning that a page may be larger than the size of the cover. Fold outs may have writing on both sides.
  • Inserts may be present and can occur in all shapes and sizes. They may be scattered throughout the volume or may be all inserted at the start or the end of the volume. Is their current position in the volume indicative of where they should appear within the page turning application? Should they be photographed in situ (difficult if they are folded and are larger than the volume) or removed from the volume for photography? Should they be displayed as part of the page turning application or as separate (but related) items within the interface?
  • Archival volumes may not all be in one piece. The original cover for the volume may have been separated from the pages. The pages may be loose. Should the page turning application display these volumes as they exist today, or attempt to reconstruct the volume as it once was?

There are lots of different ways we could address these challenges. Here is a summary of some of the lessons we have learnt:

  • Thoroughly assess the physical copies before digitisation commences - having an idea of what challenges you will encounter will help. It is best to work out a strategy for the volume as a whole at the start of the process and have to image the volume only once, rather than have to go back and re-image specific pages (bearing in mind you will need to try and ensure any new images are consistent with the previous ones to ensure a good page turning experience for the end user). If you come across fold outs, inserts or holes, decide how you are going to image them.
  • As part of this assessment process, seek the help of a conservator if there are pages for which a good image could not be easily captured (for example if a corner of the page is folded over and obscuring text). A conservator may be able to treat the document prior to digitisation to enable a better image to be captured.
  • Choose a background that will be suitable for the whole volume and stick to it.
  • Crop images to the spine of the book but with a small border around the other edges of the page. Try to keep a consistent crop size for the resulting images, but accept the fact that where there are fold outs or large inserts, the image will have to be larger. A good page turning application should be able to handle this.
  • Different page turning technologies will be able to support different things. Work out what technology you are using and know its capabilities

The last point to make is that we should not focus solely on dissemination. Image dissemination strategies, tools and applications will come and go but ultimately when you are taking high quality digital images of archives you will need to maintain a high resolution preservation version of those images within a digital archive.

An insert found within Visitations Court Book 2 - should this be
photographed within the volume or separate from the volume?
These preservation images will be around for the long term and can be used to make further dissemination copies where necessary. Think carefully about what is required here and remember to save your preservation originals at the right point within the workflow (for example once the images have been checked and a sensible file naming strategy implemented, but before any loss of information or degradation in image quality occurs). 

Also think about what other images may be needed to fully record the physical object for preservation purposes. It may be necessary to take some images that would not be used within the page turning application but that record valuable information about the physical volume. For example, the spine of the book, or a small detail on the cover that needs to be captured at a higher resolution. 

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