Computational flattening algorithms have been successfully applied to X-ray microtomography scans of damaged historical documents, but have so far been limited to scrolls, books, and documents with... Show moreComputational flattening algorithms have been successfully applied to X-ray microtomography scans of damaged historical documents, but have so far been limited to scrolls, books, and documents with one or two folds. The challenge tackled here is to reconstruct the intricate folds, tucks, and slits of unopened letters secured shut with “letterlocking,” a practice—systematized in this paper—which underpinned global communications security for centuries before modern envelopes. We present a fully automatic computational approach for reconstructing and virtually unfolding volumetric scans of a locked letter with complex internal folding, producing legible images of the letter’s contents and crease pattern while preserving letterlocking evidence. We demonstrate our method on four letterpackets from Renaissance Europe, reading the contents of one unopened letter for the first time. Using the results of virtual unfolding, we situate our findings within a novel letterlocking categorization chart based on our study of 250,000 historical letters Show less
A special interest in optics among various seventeenth-century painters living in the Dutch city of Delft, has intrigued (art-)historians for a long time. Equally, the impressive career of the... Show moreA special interest in optics among various seventeenth-century painters living in the Dutch city of Delft, has intrigued (art-)historians for a long time. Equally, the impressive career of the Delft microscopist Anthony van Leeuwenhoek has been studied by many historians of science. However, it has never been investigated who, at that time, had access to the mathematical and optical knowledge necessary for the impressive achievements of these Delft practitioners. We have tried to gain insight in Delft as a ‘node’ of optical knowledge by following the careers of three minor local figures in early-seventeenth-century Delft. We argue that through their work, products, discussions in the vernacular and exchange of skills, rather than via learned publications, these practitioners constituted a foundation on which the later scientific and artistic achievements of other Delft citizens were built. Our Delft case demonstrates that these practitioners were not simple and isolated craftsmen; rather they were crucial components in a network of scholars, savants, painters and rich virtuosi. Decades before Vermeer made his masterworks, or Van Leeuwenhoek started his famous microscopic investigations the intellectual atmosphere and artisanal knowledge in this city centred on optical topics. Show less
