Have multispectral camera, will travel!

The Alexander Pope project continues this week.  We are back at the Yale Center for British Art to do some scientific imaging on the marble bust of the poet Alexander Pope by the artist Louis Francois Roubiliac.  Ruggero Pintus and Ying Yang, Postdoctoral Fellows at the Computer Science Department, are using the Imaging Lab QSI multispectral camera and a xenon light to measure the quantity of electromagnetic radiation that is reflected by the material of the bust.  They will take a total of 8 images from every angle: 1 from the UV (ultraviolet) range, 6 from the visible light range, and 1 from the IR (infrared). Each series of 8 photographs is a more accurate way to acquire the optical properties of the studied object as opposed to an average photograph which only retains information from the red, blue and green spectrums.  This information will give conservators the proper tools to study the spatial variation of the material properties.

Ruggero Pintus describes a multispectral image as one that captures image data at specific frequencies across the electromagnetic spectrum.   Spectral imaging can allow extraction of additional information the human eye fails to capture.  Multispectral imaging aims at providing a description of the reflective properties of a surface.  Multispectral images provide a more precise color analysis which makes these images suitable for the monitoring or restoration of artwork as well as any research activities that require high quality color information.

Ruggero Pintus and Ying Yang, Postdoctoral Fellows for the Computer Science department, set up the multispectral camera and xenon light to take multispectral scans of the Alexander Pope bust. They will be measuring the quantity of electromagnetic radiation that is reflected by the material of the bust, which in this case is marble.

Ying prepares to calibrate the multispectral camera and xenon light by using the color chart and silver ball.

In this photo, the bust is being illuminated with a xenon light source, that emits light from ultraviolet, visible and infrared bands. Each spectral band contains a continuous range of wavelengths. For each band, Ruggero and Ying will measure the quantity of radiation that is reflected by the material. This will allow them to study the geometry and optical properties of the bust.

Ying rotates the bust in preparation for the next set of photos.


Nubian artifact project

This week in the Imaging Lab, the Yale Peabody Museum is collaborating with the Near Eastern Languages and Civilizations department (NELC) to photograph Nubian artifacts for documentation purposes.  NELC will be using Project Room 3 and the Hasselblad camera on the vacuum copystand to take high resolution photos of the artifacts.  This equipment allows them to get highly detailed images that can be used for publication purposes.  They will also be scanning old documents and maps related to this collection.  Here is a little background on the project:

The Toskha Project

In 2008, the Yale Peabody Museum of Natural History in collaboration with the Yale Egyptological Institute in Egypt (NELC department) began a re-examination of the material from Nubian cemeteries of the so-called Simpson Collection.

In 1962, as part of the UNESCO Nubian salvage campaign, the Pennsylvania-Yale Expedition to Egypt excavated several archaeological sites in the area of Toshka. This expedition, directed by William K. Simpson professor of Egyptology, was a component of a larger campaign carried out between 1961 and 1963 that examined the region of Toshka and Arminna in Lower Nubia. Nubia is a region along the Nile river located in southern Egypt and northern Sudan.  Several monographs resulted from this work, however, much of the archaeological material—particularly the Nubian Bronze Age cemeteries—remains unpublished.

The imaging project aims to produce a monograph with a systematic catalogue of graves and funerary offerings from Toshka West (TW) Cemeteries B, C, and D, the site of Gebel Agg at Toshka East (TE), and miscellaneous sites.

General information on burial ground and graves, including a sketch of shaft and inhumation, has been obtained from the original field notes, now housed at the West Campus Peabody Anthropology unit as part of the Simpson Archive. There are maps, photos and a few drawings from the original archive. The new high resolution photos of pottery vessels and jewelry, once part of the funerary offerings, are being taken to improve the quality of the documentation.

West Campus Peabody Anthropology unit:  Roger Colten, Maureen White and Rebekah DeAngelo

Egyptology:  Maria Gatto, Colleen Manassa and Alberto Urcia

Alberto Urcia is the digital surveying and virtual archaeology expert of the Yale Egyptological Institute and the person in charge of photographing the objects.

Nubian artifacts from the Anthropology division of the Yale Peabody Museum waiting to be photographed.

Alberto Urcia, Associate Research Scientist for Yale Egyptological Institute, manually adjusts the camera to make sure that certain areas of the artifact are in focus.

In an effort to remove shadows from the photograph, Alberto lights the artifact with an additional light source.

While normally used to shoot straight down, the camera on the vacuum copystand has been rotated 45 degrees to photograph the sides of all of the artifacts.

Alberto checks the clarity of the high resolution photograph. High resolution photographs allow researchers to view scratches, cracks and traces of paint at a high magnification.




Have 3D scanner, will travel!

We have another exciting project this week!  We packed up the ShapeGrabber 3D scanner in the YDC2 Imaging Lab and set up shop temporarily at the Yale Center for British Art where Ruggero Pintus and Ying Yang, Postdoctoral Fellows for the Computer Science department, performed 3D scans of a marble bust of the esteemed poet Alexander Pope.

3D laser scanners are best for capturing surface topography.  The scanner passes a laser beam over an objects surface rapidly to take measurements from many location points on the object.  The resulting dense grid of 3D points is called a ‘point cloud’.  This ‘point cloud’ requires post processing to convert it into a useable format.   An accurate 3D reconstruction can help authenticate works of art and can be a valuable tool for conservators.

The Yale Center for British Art (YCBA) and Waddesdon Manor (the Rothschild Foundation and the National Trust) are co-organizing a major exhibition on the sculptural images of Alexander Pope, which will open at the YCBA in spring 2014 and at Waddesdon Manor in summer 2014.  The focus of the exhibition will be the series of busts of Pope made by the French émigré sculptor Louis Francois Roubiliac. The exhibition will assemble the signed and documented versions of Roubiliac’s busts of Pope, which span the years from 1738 to 1760, as well as a number of the adaptations and copies that were modeled after them.

By performing 3D scans of all of the busts, the YCBA’s aim is to explore not only the complex relationship between these various versions but also to shed new light on the hitherto little understood processes of sculptural production and replication in eighteenth-century Britain. The project offers a unique opportunity to study the objects side by side, both visually and technically, revealing similarities and differences in handling, surfaces, dimensions, construction, and materials.

The ShapeGrabber packed and all ready to go to the Yale Center for British Art to begin scanning!

Ruggero Pintus rotates the bust of Alexander Pope a few degrees so that the camera can acquire a new scan.

The scanner is placed level with the bust to get straight on scans of the bust.

Close up of the laser sweeping over the bust as it completes a scan.

Ying Yang checks to make sure the new angle of the laser is capturing the data from the underside of the bust. By lowering the scanner and angling the laser up, scans of the underside of the shoulders, chin, nose and ears of the bust can all be captured. The data in these scans will then be aligned with the data from the scans taken with the camera level with the bust.

Ruggero looks on as the laser acquires data from scans of the top of the bust. By moving the scanner to a higher position, the laser is now able to scan the top of the shoulders and the head of the bust. The scans of these areas will be added to the scans from the other two positions and will be compiled into a digital 3D rendering of the Pope bust.

Ying and Ruggero align and combine all of the scans to produce a 3D image of the bust.