Photogrammetry in the library: digitising the Ehrenberg bequest

Barbara Roberts (Winnington-Ingram Graduate Library Trainee) reports on an event hosted by the Combined Library of the ICS and the Hellenic and Roman Societies, at which participants collaborated to produce digital images of objects in the library’s collection.

On an evening in November, students and staff assembled in the Combined Library of the Institute of Classical Studies and the Hellenic and Roman Societies for a photogrammetry sprint using artefacts from the Ehrenberg bequest. ‘Photogrammetry’ is, in general, the use of photographs to take measurements. In our case this was to make 3D models of the objects. This involved several steps. The first consisted of taking numerous photos (at least 40 were recommended) from all angles of one object, using a digital camera or a smartphone. The object itself had to remain completely stationary. The aim was to make sure that every area on the surface of the object had been photographed. This necessitated some creative camera positioning on the part of the photographer, given that the object could not move and that some areas on the objects, like spaces underneath vases’ handles or drapery on statuettes, were hard to reach.

Then all of these photos were uploaded to AgiSoft PhotoScan, the photogrammetry software installed on the library PCs, for several stages of processing. These ranged from image alignment to having the software build a ‘mesh’ of the surfaces detected. Inadvertently, many of us had managed to include enough photos of the library in the background for it to be included in the mesh, too. In other cases, we hadn’t managed to photograph all the nooks and crannies in the object, leaving the 3D mesh with holes or some rather improbable geometries.

For a more detailed summary of the workflow involved in this process, including the possible application for the data produced in 3D printing replicas of objects, you can turn to this blogpost by Gabriel Bodard. Use of this sort of photogrammetry is widespread among many major museums in the UK. For example, the British Museum and National Museums Scotland run Sketchfab accounts allowing access to many of their holdings (see here and here).

This event was, for many of us, a first interaction with the world of 3D modelling and its applications to studying the ancient world. The greater accessibility these models gave to an object no longer physically in front of us and able to be inspected at every angle was apparent.  It was also just one of several attempts in the past to catalogue and document the collection that began with Ehrenberg himself. The Library possesses Ehrenberg’s handwritten catalogue of the objects, donated by his son in 1998. They consist of handwritten notes describing the appearance, dimensions, provenance and approximate centuries of manufacture of each individual object. While some entries come with black-and-white photographs, the majority are illustrated by hand-drawn sketches in pencil or pen and ink.

Victor Ehrenberg was a German historian of the ancient world active for much of the twentieth century, who had moved to Britain with his family on the outbreak of war in 1939. After teaching in an independent school for a few years, he became a Lecturer in Ancient History and Greek at King’s College, Newcastle-upon-Tyne (now part of the University of Durham) and then a Reader in Ancient History at Bedford College, University of London (now part of Royal Holloway). His work concentrated on Greek history in the classical and Hellenistic period This is reflected in his most recognised work today, From Solon to Socrates: Greek History and Civilisation during the Sixth and Fifth Centuries BC. On his death, his collection of antiquities were left to the Institute of Classical Studies for study and display, particularly by students of King’s and Bedford College and within the Institute itself. They are now located in display cases towards the back of the Archaeology reading room. They form part of a larger bequest by Ehrenberg to the Institute which included correspondence, notes and other papers produced throughout his life. More information on Ehrenberg’s life and the archive as a whole can be found here.

An undated typewritten report on the collection of antiquities, presumably from the 1980s or 1990s, states, “This was the private collection of Victor Ehrenberg and was left to the Institute of Classical Studies in 1976 for display and for study by the students of the University. It consists of 155 small objects, ranging from the Minoan/Mycenaean to Byzantine periods, and is stored in the library. Of the better preserved objects, 41, including statuettes and vases, are displayed in specially designed glass cases. Most of the remainder are sherds. There is a catalogue of the complete collection.” The catalogue mentioned at the end survives in the Library’s archives. It consists of similar measurements and photographs to the notes, but with photographs of higher quality taken at multiple angles.

These three attempts at describing the objects each ended up gathering different information (fig. 1). This can best be illustrated by comparing their documentation of one object. The object, pictured here in its display case, is a black-figure lekythosnumbered as no. 2 on Ehrenberg’s and the library’s catalogues (fig. 2). The text of the two catalogue descriptions is very similar – both describe a “Black figure lekythos. Agon of hoplites, with two umpires. An over-lengthened cock on shoulder. Attica, early 5th cent. Spout and foot restored. Height: 14cm = 5½.” The Ehrenberg catalogue expands on the provenance (“bought at Athens, 1925”) and cites another image of the object published in one of his books, Society and Civilization in Greece and Rome (fig. 17 in that volume), both of which add something to the object’s history. Handwritten addenda also correct earlier statements like an earlier dating to circa 500 BCE.

The 3D model is less informative on matters of material and provenance, but allows a viewer to access all angles of an object rather than just those photographed (fig. 5). The quality of the image produced also depends on the use of high-quality photography and lighting equipment, but as the sprint showed, we were able to produce some impressive results with just a phone camera, no extra lighting and the processing powers of the library machines even within the hour or so the workshop lasted. It also meant that anyone with access to the image file, once it had been cleaned up a little, would be able to inspect and even 3D print replicas of the object, no matter how far from the original they were. Not only that, but with it the viewer can look around, behind and even (to an extent) underneath the object, something not even possible in person. The access this grants has, unsurprisingly, been embraced by museums looking to enhance the way they display their objects. It ought also to help researchers access otherwise hard to reach objects, and allow for more people to look at and interpret the same objects, meaning that with enough resources, reference or study collections like the Ehrenberg bequest might be able to educate even more people than their original intended audience.