Projects: Center for Scientific Studies in the Arts

About This Project

Computational imaging allowed us to evaluate the surface structure of Gauguin’s graphic production with the aim of better understanding his printmaking and transfer processes. We captured sequences of photos from known lighting directions and used these photos to separate color from surface shape with photometric stereo. The data we obtained gave us new, and never-before-seen, visual documentation and insight into how Gauguin formed, layered, and re-used imagery interchangeably to make these works. Based on these measurements, we reconstructed his printmaking and transfer techniques and so firmly established how Gauguin approached the art-making process in these varied works of art on paper.

Background

Paul Gauguin is perhaps one of the most well-known of the Post-Impressionist artists working in the late 19th century. He was born in Paris in 1848 and died in the Marquesas Islands in 1903. His paintings are inhabited by Bretons, and later, Tahitians, surrounded by the flora and fauna of what Gauguin saw as an exotic, primitive and pure land on the shores of the South Pacific. Using a colorful palette and broad brushstrokes, he brought these lands to life. Less known are his many graphic works – the focus of this internal research project. Gauguin was an academically untrained draftsman and printmaker – free to be highly experimental with the materials and techniques that he used to make unconventional prints, monotypes and transfer drawings. To this day art historians and conservators puzzle over them.

Nativity: A Case Study

Gauguin’s Nativity served as our case study. It is a so-called “oil transfer drawing” on paper that the artist produced in 1902 using a transfer process that had perplexed conservators and art historians. At first glance, the print looks like it was made by the simple monotyping method. Upon closer inspection, however, it became clear that Gauguin’s printmaking process was more complex.

The "blind incisions"

Focusing on the section with a woman cradling a child, we noticed that several regions contained lines where no ink or pigment had been applied. For decades, these features have been noted by art historians, who theorized that they’d been caused by so-called “blind incising” – indentations in the paper where ink simply wasn’t transferred - but it has always been unclear how these incisions were introduced during the printmaking process.

Initial ideas

In the photometric stereo image of Nativity, we clearly saw indisputable evidence of the ink being transferred onto the print using traditional monotyping. However, for the areas of blind incision we expected to see an indentation in the paper corresponding to what we thought was Gauguin’s technique: drawing on a stack of papers and transferring impressions of his drawing to sheets below. The expected topography, however, was not observed at all, as seen in the image above, confirming that the "blind incisions" could not have been made by impressing the paper.

The Answer

After observing a mapping of the all blind incisions, depicted above, a new idea emerged: we were looking at impressions made from the inked surface, rather than elements contained in the paper. We developed a new hypothesis that Gauguin used a hard and flat material (such as a glass slab), covered it in ink, and then created multiple monotypes of different images from this inked matrix. In doing so, he left behind a palimpsest of un-inked areas from earlier drawings that would be transferred onto a piece of paper as blank lines with no surface topography.

What is Computational Imaging?

Computational imaging, essentially a merging of computer science with photography, is a vital aspect of this project that allows for the reconstruction of 3D shapes even on a minuscule scale. Professor Oliver Cossairt specializes in this area of research and has focused on developing cameras capable of visualizing information beyond the limits of what the human eye can perceive. This technology is a highly valuable resource for deciphering Nativity.

Computational Imaging Provides the Answers

Photometric Stereo

Photometric stereo allows researchers to view the topography of an object (in this case, an art print) by separating color from surface shape. In doing so, an object’s topography can be measured from the small changes in brightness that different lighting directions may cause. Take a deeper look into how light plays a key role in 3D shape recovery.

Capturing Gauguin's Nativity

Our photometric stereo setup consists of a color checker for color calibration, a 3D calibration target for 3D surface calibration, a reflective sphere for calibrating light direction, and the work of art. We captured a sequence of photographs of the artwork from a fixed camera location while changing the direction of the light source. This allowed us to calculate the surface normal at each point by solving a system of linear equations from our set of measurements at each pixel.

Surface reconstruction precision

The image above is a comparison of the 3D reconstruction with the 3D calibration target. The height of the cone in the calibration target is approximately 10mm. The surface reconstruction of Nativity indicates that its protruding lines are approximately 100 times smaller, which means that they are on the order of 100μm in height.

Surface shading for transferred lines

The image above shows a comparison of the original Nativity with its surface shading information corresponding to transferred lines. As seen in the image, the transferred lines show clear evidence of surface shapes that protrude from the page, confirming the use of traditional monotyping.

3D surface shape animation of transferred lines.

The image above is a still from an animation visualizing the 3D surface shape at the location of the lines drawn in Nativity. We magnified the area with the transferred lines along with a few frames of a 3D animation. As we peel off the color and shift perspective to look at the 3D surface shape, we see clear evidence of protrusions on the page where ink has been deposited. This is solid evidence of the ink transfer from a matrix such as that in a monotype transfer process.

Surface shading for “blind incising.”

The image above compares the original Nativity with its surface shading information corresponding to the blind incisions. The comparison clearly shows that there are no surface features at the locations of the blind incisions. This solid evidence supports the conclusion that the blind incisions did not originate from any indentations in the paper surface during ink transfer and it, therefore, supports the hypothesis of Gauguin's technique using an inked matrix.

Reproducing Gauguin's Prints

To confirm our hypothesis, we replicated this process by recreating prints with ‘blind incisions’ that match what we found on Nativity, even at microscopic magnification. When comparing Gauguin’s Nativity and the transfer drawing produced using our hypothesized transfer process, it can be seen that the marks on the reconstruction appear visually consistent with the original.

The Traditional Method

First, a standard monotype is made by placing a piece of paper on an inked surface (the glass matrix) and drawing on the back. The monotype produced is removed from the glass matrix and set aside. Now the glass matrix lacks ink in the locations where it was transferred to the first monotype.

Gauguin's technique

We then place a second piece of paper on the same inked surface; this piece of paper will eventually be our final transfer drawing. We then draw on the back of this sheet of paper to transfer the initial ink layer, which in this example, is brown. When we lift our sheet of paper from the matrix, we see that we have transferred inked lines to the surface, but the lines are broken in locations where ink was previously removed from the matrix while creating the first monotype.

The Final Product

We then place the same sheet of paper that now carries a brown ink impression onto a second glass matrix inked with darker pigment. This matrix is pristine. We again draw on the back of the sheet to transfer the darker lines that form the second layer of transferred media. When we remove the paper, the process is finished and we have created the final transfer drawing. As seen in the comparison above, the marks on the reconstruction (right) are visually consistent with the original (left).

Related Talks and Project Media Coverage

Publication:

"Surface Shape Studies of the Art of Paul Gauguin" , O. Cossairt, X. Huang, N. Matsuda, J. Tumblin, A. Katsaggelos, D. Kronkite, G. Bearman, H. Stratis, M. Broadway, M. Walton, Digital Heritage Granada Conference, September 2015.

Presentation at the AAAS Annual Meeting on Information, Innovation, and Imaging, 2014:

“Surface Shape Studies of the Art of Paul Gauguin,” O. Cossairt, X. Huang, N. Matsuda, J. Tumblin, A. Katsaggelos, D. Kronkite, G. Bearman, H. Stratis, M. Broadway, M. Walton.

RTI and Paul Gauguin: Summer Research for Teachers With The Center for Scientific Studies in the Arts:

Carla Stone, a Golden Apple 6th grade Science and Social Studies teacher at Martin Luther King Literary and Fine Arts School in Evanston, shares her summer experience shares her summer experience with the Research Experience for Teachers program at Northwestern University. Stone's research focused on using RTI on Paul Gauguin's prints to better understand his process during their creation.

Newsweek coverage >

The Conversation coverage >

McCormick School of Engineering coverage >

Northwestern University video >

Additional national and international coverage >

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