Tag Archives: Reflective Transformation Imaging

Exploring 3D technologies at the BPMA

The last 12 months have been exciting for the Digital team here at the BPMA. Our Share Academy/London Museums Group funded project, From Vault to View, which partnered us with Mona Hess from UCL’s Civil, Environmental and Geomatic Engineering Department, has given us both a lot to do and to think about. The project has now come to an end, but it has increased the knowledge we now have of 3D technologies, and encouraged us to do much more.

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George V Die for striking leads. 1½d postage British Empire Exhibition, 1925

The aim of the project was to test different methods of capturing objects in 3D. Working with our little-viewed objects, Mona tried a variety of techniques to see what would produce good 3D models and what wouldn’t. The objects chosen posed real challenges: many were made of bright metals, which makes them difficult to capture using laser scanning or photogrammetry techniques; some were complex shapes, such as a flintlock pistol; while others had such a lack of detail making them difficult to measure and recreate as 3D computer models.

So what did we get out of it? Before the project we knew very little about how 3D

imaging worked. We felt the buzz around these technologies, such as 3D printing, but had little idea of how these things were created or how they might be used. All we really knew was that we had a rich treasure of 3D objects that no-one could really access physically in a satisfactory way.

By the end of the project, the BPMA had purchased photogrammetry software which has enabled us to try 3D imaging for ourselves – and the results are extremely promising. These techniques can be learnt by our staff and employed to create 3D models of items in the museum collection for exploration by the public.

This new-found knowledge, though still fairly elementary, has given us confidence to explore other uses for 3D imaging. In December 3D experts, ScanLab Projects, spent a week scanning the work depot, platforms and tunnels of Mail Rail which we will be opening to the public in 2016 as part of our plans for The Postal Museum. The results are truly astounding and we hope to show them in the near future.

Scanner capturing Mount Pleasant platform

Scanner capturing Mount Pleasant platform

Beyond all this, the project has given us an opportunity to revisit the objects and see them afresh. Although we weren’t able to obtain good 3D models of objects such as the large printing plates and the rollers, we did get excellent images of a number of dies using a technique known as Reflectance Transformation Imaging [RTI]. We also obtained an excellent laser-scanned 3D model of the Machin cast of Queen Elizabeth II – a truly unique and iconic object. The fruits of these experiments will eventually be made available via our website and online catalogue as we integrate the technology.

Plaster head of HM the Queen made by Arnold Machin for new definitive issue of stamps, third version (POST 118/5373)

Plaster head of HM the Queen made by Arnold Machin for new definitive issue of stamps, third version (POST 118/5373)

-Martin Devereux, Head of Digital

3D Scanning moves into its final phase

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.

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Scanning the flintlock pistol.

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/

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Scanning at UCL

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.

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Latest tests at the BPMA

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.