Working with Imperfect Manuscripts: Image Manipulation in MSR

MSR uses images from documents produced by Church of Scotland presbyteries between 1560 and 1689 to gather data on clerical careers. Indeed, at the time of writing, we have read over two and a half thousand pages of such material. And we aren’t finished!

Our friends at the National Records of Scotland provide us with bulk deposits of images of these manuscripts, presbytery by presbytery. These images were taken between 2003 and 2005, during which time around five million document images were snapped and digitised. These images form a terrific resource that can be accessed via the Virtual Volumes system at the National Records of Scotland reading rooms in Edinburgh. Due to bandwidth constraints in the early 2000s, these images were taken at a resolution of 2174 × 1655 pixels, or just over 3.5 million pixels per image. By contrast, images snapped on a current mobile phone camera can hit around 12.1 million pixels per image. These technical constraints and the fact that our manuscripts were produced four centuries ago and survive in varying states of decay means that our source base can be quite difficult to read. This blog post will take you through some of the methodologies we use to enhance the amount of data we can recover from our source base.

The following image is from a particularly faded section the records of Dalkeith Presbytery from 1614 (NRS, CH2/424/1). One can observe how the marginal annotation appears in a much deeper ink on the left-hand side, but the main entry to the right is faded. Moreover, some of the ink from the other side of the manuscript is just starting to bleed in to cloud our vision further. While this isn’t the worst manuscript pre-modern historians are likely to see (!), this is a common trait of some of the volumes with which we work.

Any illegible part of a manuscript is irksome, but it is particularly annoying in projects like ours that rely on parsing large numbers of manuscripts each day. Moreover, the early part of the seventeenth century was when Dalkeith Presbytery became far more active in recording details of clerical careers (among other things), so it is essential that we capture this data. 

Fortunately, there are a number of simple techniques that historians can use to improve their chances of seeing through this sort of haze. In particular, we can manipulate the colour balance of the image to bring the text into greater relief using quite basic computer software. Here’s one example with the image contrast boosted and with exposure increased. I think this setting allows manuscripts to appear as my family expect them –  suitably old – but it also allows the ink to become far clearer to the naked eye.

The next example saps most colours from the image to bring darker colours into greater relief. Such methods can also produce the dreaded white-on-black images that you might remember from older microfilm scans. Nevertheless, this approach can reveal obscured letter forms and even obliterated text.

With higher resolution images than ours, the amount of detail captured by a more modern camera’s sensor will allow for potentially better results. But at 3.6 megapixels, I’m quite happy with the results we’ve obtained here.

There are a number of different methods scholars can use to get these results, some more computationally intensive than others. The first is to use in-built image editing software that comes bundled with most consumer computers. For example, the app Preview in MacOS has an ‘Adjust Colour’ feature in its ‘Tools’ menu. Similar tools are available in the Photos app on Windows.

The key options here are the contrast and exposure sliders, that will allow you to adjust image accordingly. The sliders at the top of the menu allow manual adjustments so you can emphasise particular colours. 

More specialist software packages offer more powerful tools that can be used to target certain problematic areas of a manuscript image, rather than affecting the entire image. Software packages like Adobe PhotoShop and the cheaper Pixelmator are understandably associated with commercial enterprise work but can be used fruitfully by scholars to improve the visibility of problematic manuscripts. In particular, these software packages offer tools that will metaphorically ‘burn’ areas of the manuscript in order to raise faded text into a darker, more readable, form. Here’s a video of our manuscript sample from Dalkeith Presbytery again, this time being ‘burned’ in Pixelmator:

The more times the user passes the cursor over the chosen area, the deeper the darkening effect will become. Changing the ‘Exposure’ (or ‘Opacity’) setting (at the top of the screen in the video) allows the user to adjust the strength of the effect. While this is a time-consuming process, it can serve to reveal details in manuscripts that would have been too faded to enter into our analysis. It is an ideal approach for small-scale repairs to areas of the source base.

Such is the power of online computing that there are some online tools that can process images in equally powerful ways. The website Retro Reveal runs a number of image processing algorithms that are tuned to bring the sorts of text one might find in manuscripts into greater relief. While Retro Reveal is more suited to looking for very specific details in manuscripts, it can prove useful for generating alternate versions of large manuscript images, too.

These techniques are part of MSR’s daily toolbox to help us navigate the world of Church of Scotland presbytery manuscripts from between 1560 and 1689. We wanted to share our experience because these approaches will be of interest to other scholars working with manuscript images, but they will also be largely hidden when our dataset is released into the wild. When viewing MSR’s dataset, it is effectively naked and extracted from its physical context of the manuscript in which it exists. It is easy to forget that each entry in our database involves numerous steps of discovery, manipulation and manuscript analysis.

Chris R. Langley

Leave a Reply

Your email address will not be published. Required fields are marked *