Building an Image Bank of Inscriptions
The imaging project for inscriptions developed out of an initiative to reorganise and catalogue Oxford University's squeeze collection and make it accessible as a research resource to the widest possible audience. The project draws its inspiration from the work undertaken at Michigan and Duke universities within the framework of APIS to create a unified database of papyrological resources including texts and, above all, images.
The requirements of an image database of inscriptions differ from those of a papyrological image bank in a basic respect - inscribed documents are in general much larger than written papyri. This makes it both possible, while retaining the advantages of the digital medium, and, indeed, necessary, in order to keep image sizes within manageable limits, to capture images at a lower resolution than the 600 dpi archival standard prescribed by APIS for papyri.
During the initial experimental stage of the project images were captured at resolutions of 150 dpi and 300 dpi. 150 dpi images were found to be adequate for most scholarly purposes, but, in order to ensure that the images in the database remain useful for as long as possible, it was decided to set the higher resolution as the standard to be used in the main phase of the project, when representative corpora of images would be built up. All scans are now made at a minimum resolution of 300 dpi. Images are taken directly from squeezes using UMAX Powerlook A4 and Epson Expression 1640XL Pro A3 flatbed scanners and PowerMacintosh 8100 and G3 computers. Images of inscriptions larger than the scanning area are stitched together from separate scans made using the same settings. Minor adjustments for contrast are made in Adobe Photoshop 6.0. Photoshop's Unsharp Mask filter has been applied to the scaled down derivative images available in the image database, but not to the original scanned images, which are archived on the University's Hierarchical File Server in uncompressed TIFF format. Experiments at photographing squeezes have also been carried out using the Centre's Leaf Lumina digital camera, but, although the results were satisfactory, the flatbed scanner remains the preferred method of capturing images of squeezes.
The primary images acquired for the database will be taken from squeezes. Because these are a secondary medium, the basic images contained in the image bank will necessarily be at least two stages removed from the originals that they represent. A squeeze, moreover, can represent only the inscribed face of an inscription. In a field of study in which mistakes can follow from inattention to the physical context and character of a document, these are potentially serious limitations to the scope of the database. Wherever possible, therefore, images of squeezes will be supplemented by photographs of the original monument. For studying the inscribed text itself, however, images of squeezes have considerable advantages, because they can be captured in controlled conditions and at a uniform scale. It is for this reason that they form the primary focus of the Centre's epigraphical imaging project.
The quality of the image will depend naturally on the quality of the squeeze, which, in turn, will reflect the preservation of the inscribed surface. The majority of the images presented here are taken from good squeezes, but in the case of OGIS 78, although the result is very useable, the difficulties of representing severely eroded surfaces are beginning to become obtrusive. It may be that image enhancement techniques will eventually have to be used to provide acceptable representations of particularly difficult texts. This is an issue that is at present under consideration.
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Last updated on Wednesday, 30 January, 2002: 09:22:55