Over the last fortnight we have been undertaking the latest stages of scanning of our 3D philatelic objects as part of our Share Academy funded project – from vault to view.
We took a number of dies, including the Old Original die of the Penny Black, and the Silver Wyon Medal, over to UCL to be photographed in a PTM dome. The dome is opaque and is fitted with 84 flash lights arranged in rings around the hemisphere. Each flash is activated one at a time and a photograph taken. Once all 84 flashes have been triggered the resulting 84 photographs are processed together into one image so that all the lighting conditions can be observed via a special viewing computer program. The observer can manipulate the lighting condition to reveal hidden features – the engraving, the scratches on a die, etc
The activity described above is part of a series of techniques for a process known as Reflective Transformation Imaging (RTI). You can find out more here – http://culturalheritageimaging.org/Technologies/RTI/
The results of this test are still being processed, but the images we’ve seen so far are impressive and we’re very excited by them.
Last week UCL’s 3D specialist, Mona Hess, visited the BPMA bringing a portable 3D laser scanner with her. This was to be the last set of trials with laser scanning and we wanted to try the same set of objects which were digitised by the PTM dome. This time around, the results were more mixed as the laser had difficulty with the shiny surfaces of the dies and medal. We also tried scanning the flintlock pistol we had scanned previously with the large laser scanner at UCL and the results were slightly better. The scanner rendered the wooden parts of the handle and stock, but struggled to render the metallic parts, such as the barrel and the firing mechanism.
The preliminary findings of the tests show that the PTM dome renders the most useful images of metallic objects from the stamp printing process. We have one day of scanning left to complete in this fascinating project and we will then make the results of the whole project publicly available.