The basics
We use a stand-mounted digital camera to capture images of the Oxyrhynchus Papyri. The camera setup consists of a high-quality studio camera body with Phase One imaging gear fitted to the back, taking the place of the film holder. The Phase One gear is run via software on the Mac G3 we also use for web design. Thanks to a generous grant, we are now in the process of acquiring new equipment which replaces older, borrowed gear:
- the G3
- a massive new floor-standing camera stand, making it possible to image larger papyri in one shot
- a powerful new lighting system, with greater flexibility in positioning
- a larger lightbox, with adjustable brightness, offering more even backlighting
The standard lighting setup for the images taken so far has consisted of fluorescent tube units mounted on adjustable rails above and to the sides of the stand base. The papyri housed in the Ashmolean are kept sandwiched between sheets of glass, secured together with masking tape, and we do not tamper with this protection during photography. This glass can lead to a number of problems:
- Glare - light reflects off the glass: this sets limits on how we can light the image.
- Shadows - the papyrus is several millimeters above the base of the camera stand: the shadows it casts on the base can be highly distracting.
- Focus - the glass varies in thickness, the frames more so (depending on how many thicknesses of masking tape hold them together), so the camera focus must be frequently adjusted.
- Dirt - papyrologists have grubby fingers. We often have to scrub the glass before we can acquire an acceptable image. Some of the glass was formerly part of Revel Coles’s greenhouse.
The best compromise we have been able to come up with is this: the glass frame is placed on a lightbox offering muted backlighting: this shows up holes and edges sharply, minimises shadow effects, and can help distinguish between ink traces and material flaws in the papyrus. The proposed new lighting rig should help cut shadows further.
What are we trying to achieve?
This project is in many ways inspired by the striking success of American APIS imaging projects. APIS participants have committed themselves to a closely reasoned and interconnecting set of goals:
- Produce high-quality digital images for archiving
- Provide useful images over the Internet
- Associate every image with the data users need, in searchable form: eg
- MARC library records
- SGML databases
- HTML databases, searchable by CGI engines
Acquiring high-quality images is the first priority — and a time-consuming process. Securely archived TIFF images ‘future-proof’ the actual collection (fingers crossed it won’t go up in smoke, but it could). Made available to individual scholars, they reduce wear on fragile originals.
But high-quality images take all day to download: the files we are archiving routinely hit around 90 mB. A single image is bigger than the entire hard drive on some older machines still in use! And the highest resolutions (thousands of dpi) are better than we need even for archiving. This makes them overkill for most useful purposes — even for quite detailed consultation. So we’re following the APIS sites in archiving sharp 600dpi TIFF images, and putting lower resolutions images online in JPEG format. 600dpi refers to an actual inch of papyus, as measured with a scale.
But...images alone are pretty useless: pretty, because papyrus is a beautiful medium, but useless, because an isolated image tells us nothing. It lacks interpretative context. So we have to work on ways of associating images with data, and making the data accessible in ways that are useful to working papyrologists. We are fortunate that the papyri we are working with have all been published in a form that is readily available to serious researchers. Nonetheless, we have to meet the online user halfway in finding a path through this mass of data to a particular item.
What are we trying to show?
The issues leading to our worries about backlighting in archive images raise the question: what is it we are trying to show? That is to say: what information do we prioritise? Conversely, what information would we happily lose, or even discard as ‘noise’? Questions of this sort can arise at a number of stages:
- when we pick a particular exposure time or f-stop (affecting depth of field)
- when we image a papyrus (and tell the camera what its parameters will be)
- when we resize or crop or (for online provision) filter that image
- when we choose a resolution for delivery
- when we choose a graphics file format (different formats produce very different effects)
A picture is worth a thousand words; but that is also to say that every picture tells a particular story. Each image is arguably an interpretation of the original artifact, which contains any number of ‘stories’. These might include:
- ink traces
- fibre structure (often very important in placing fragments)
- surface texture and general condition of papyrus
- aesthetic qualities of papyrus
- structural qualities of papyrus
- the traces of the material’s passage through time:
- reuse(s): mummy cartonnage, for one
- patterns of damage (natural history of papyrovore invertebrates?)
- patterns of accretion (taxonomy of Egyptian dirt?)
The setup(s) we choose are determined by the kind of ‘reading’ of the original we are aiming to produce. In general, academics look at papyri for texts, meaning it’s the ink traces that really count: the colour of the material, for instance, is regarded as less important. So Duke, for instance, routinely (and quite sensibly) run their images through PhotoShop’s Unsharp Mask filter, increasing the contrast to bring out the ink. We have done the same for our Web images. But colour can be important in deciding which fragments might belong together. So too can alignment of the fibres, worm holes, wear and tear. Any choice of what information to prioritise at all costs is going to be a compromise.
But the user has every right to know what choices we’ve made (or at least be given the information to make an educated guess). So we include scales in our images. This is particularly important for archiving purposes, but is pretty handy in a wider context: just how big is that papyrus? More specialised users may wish to know: how concerned have we been to reproduce colour balance accurately? (How close to ‘natural’ is our lighting rig?) Have we even focused the camera? Colour and grey scales act as a control on our images. In general, only a centimeter/inch rule is left in the cropped, resized images we put online at 150dpi, but the archived versions contain all the information for future reference.
| Camera body: | Fuji studio camera
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| Digital camera back: | Phase One unit, by PowerPhase
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| Camera software: | Phase One proprietary software
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| Computer: | now G3, formerly Motorola ‘Starmax’ PowerMac clone
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| Lighting rig: | now LARN, formerly Kaiser RB5004 fluorescent tube units
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| Scales: | Kodak Colour Control Patches, Kodak Gray Scale
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Imaging menu / Main menu / Markup