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.

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