RTI at the Cataraqui Cemetery March 27, 2010

It was a brisk Saturday afternoon at the end of March when we organized the first official day of the workshop in the cemetery. Many were familiar faces to us from the pilot project, but others were new to RTI. The overcast conditions favoured good RTI captures as the ambient light was relatively low and even.

Notice hats and gloves were necessary for the day’s work!

Some low shots using the monopod. Notice Fernando recording the process (see the end of the post of the fruits of his labour).

If you look carefully at these shots you can see a metal rod protruding from the flash along the line of the string and the cone of light (a Canadian invention, we might add)…more on the “rod technique” in a later post.

Fernando again hard at work recording the process in HD video. While it was a good day for RTI, the light conditions were frustrating for such a seasoned filmmaker.

In order to get as many light positions as possible, we have been making regular use of a step-ladder. Caution is needed, however, on the rolling terrain. As we remind the students, many of the dips in the topography represent long-collapsed coffins. It’s important to remember just where we are…

This is wonderfully clear image the rod extending from the flash to the centre of the object.

Here’s a shot of our final post-processing in the Classics Lounge in Watson Hall. We’re using a brand-new Dell M6500 Mobile Precision Workstation with a 17″ monitor and 8gb of RAM. With this, the process of fitting and manipulating Polynomial Texture Maps is a breeze. With the addition of our Intel Solid State Disk we’ve really broken the sound barrier on the assembly of large RTIs (>100mb). Notice also Sarah and Craig sporting the Queen’s colours, just in case you didn’t know this was a Queen’s University Project!

Here’s great video we put together using Fernando’s footage. Many thanks to Sara Gabova for providing the pleasant voice-over.

Thanks Fernando!

RTI at the Cataraqui Cemetery March 20, 2010

An overcast day – the perfect conditions for Reflectance Transformation Imaging acquisition. Nine students joined us from 1 to 6 pm to image 9 stones. The students were divided into two groups and produced some of the best RTIs to date. We imaged two limestone and seven marble head stones.

Here are some screen shots and comparison images:

one of the oldest stones / local limestone / regular light / specular enhancement

the bio growth and rain drops obscure some of the surface information

practically illegible stone of Philip Ferguson Hall / regular light / specular enhancement

marble insert into sandstone / Ann Jane Brown / Regular Light / Specular Enhancement

click on any of the images to view and/or enlarge them

related video from UCS ICT

Saturday and Sunday, 13 and 14 March, 2010

Unexpectedly the weather cleared in mid-March and ahead of schedule we decided to head to the cemetery with two groups of students on Saturday and Sunday. Using a single camera, battery and light we imaged four stones altogether, two per afternoon. With a group of mostly undergraduate students we managed to capture some great RTIs.

Our first candidate was a heavily weathered stone within the Sir John A. Macdonald enclosure.

We again chose to use the temporary shelter to minimize the sun on the stone. Here are the results:

The results were generally good for the stone of Professor Williamson’s first wife, Margaret Gilchrist,  but the centre of the stone was still very difficult to read, even with specular enhancement. John Granville, the National Historic Sites Program Manager (Eastern Ontario) for Parks Canada, was kind enough to give us a photo of the same stone taken in 1982. The comparison is striking…but more on that in a subsequent post.

We next turned to what we were told is the oldest stone in the cemetery, that of Mary McCrea adjacent to Sydenham Rd. Unlike many of the more expensive monuments in the cemetery, hers was made of local, Kingston limestone that has been very heavily degraded. To the naked eye much of the inscription was unreadable. Here are the results:

Although there was a small shadow at the bottom but the surface normals were still correct on the specular enhancement (image on the right).

The next day, Sunday, we brought our a group of enthusiastic students from the Masters of Art Conservation at Queen’s. We are particularly happy to have their involvement as this sort of documentation work will surely become a standard in their field. We began by imaging a stone that had quite a clear incision, but heavy lichen accumulation. Even with the lichen cleaned off, however, the mostly white granite stone of the marker made it all but impossible to read the text. Here are the results:

Again, shadows marred our final result, but the text was certainly very clear! Our second and final stone for the day was a rather sad case. A marble insert had been placed in sandstone and was buckling due to a century of thermal stress. In fact, the insert was so bowed-out that surface layers of the marble were spalling.

What became immediately clear when we processed the image was that the focus was off during the capture (mea culpa). We can see on the Surface Normal Visualization just what effect this had on the processed results (the planar surface we expect to be blue on a good capture):

We went back to this stone on a subsequent trip to the cemetery (see the next blog entry on 20 March for those results). A lesson was learned! Focus, Focus, Focus.