A Young Woman Standing at a Virginal Johannes Vermeer c L33; inv. number NG1383 National Gallery London

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1 1 WEAVE MAP REPORT A Young Woman Standing at a Virginal Johannes Vermeer c L33; inv. number NG1383 National Gallery London C. Richard Johnson, Jr. Cornell University johnson@ece.cornell.edu William A. Sethares University of Wisconsin - Madison sethares@gmail.com August 2017 In this report, paintings by Vermeer are referred to by L-numbers, based on their numbering in W. Liedtke, Vermeer: The Complete Paintings, Ludion, The dates cited on this cover page span the range of dates estimated in the oeuvre catalogs by Wheelock (1997), Liedtke (2008), and Franits (2015) as compiled in the table at references/dates.html.

2 Johnson and Sethares, Weave Map Report, August Summary This document applies spectral-based, automated thread counting to A Young Woman Standing at a Virginal (L33) by Johannes Vermeer and includes the following: 1. stitched x-radiograph of full painting 2. vertical thread density map 3. horizontal thread density map 4. vertical thread angle map 5. horizontal thread angle map 6. histograms of vertical and horizontal thread counts and angle maps 7. a listing of all close count matches (within ±1 th/cm in both directions for an H to H and V to V match or an H to V and V to H match) among Vermeer s paintings on canvas 8. a composite image containing thread density maps of the painting being studied and its close count matches to the same scale and colorbar for weave match hunting 9. image of weave match between L33 and its close count match L comments on observed cusping and weft snakes Observations: tg The average thread density of A Young Woman Standing at a Virginal is (H x V) is x th/cm. A Young Woman Standing at a Virginal has cusping of depth greater than 5 cm on one side (bottom) and cusping of approximately 5 cm in depth on the other three sides (top, left, and right). A Young Woman Standing at a Virginal has five close count matches, and a weave match with one of them. The horizontal thread angle map of A Young Woman Standing at a Virginal displays two weft snake indicators.

3 Johnson and Sethares, Weave Map Report, August Background Manual thread counting has been used for several decades. One canvas descriptor that has been routinely collected is the average thread count of the threads in each direction (vertical and horizontal) in a painting s canvas. This information has been used to discount the possibility of two canvases coming from the same original roll if their average thread counts (horizontal compared to horizontal and vertical compared to vertical or horizontal compared to vertical and vertical to horizontal) are too different, e.g. by more than 1 th/cm. In 2009, the first weave maps derived from automated thread counts based on a spectral analysis of the painting s x-radiograph were shown at the annual AIC meeting in Los Angeles. The stripes that arise in color-coded images of thread count in small evaluation squares covering the entire painting were immediately recognized as a fingerprint of a specific roll. The first weave match was also shown in this talk [1]. The utility of automated thread counting for canvases with a sufficiently regular weave was confirmed in [2]. Weave matches with art historical implications have been reported for paintings by van Gogh [3], Velázquez [4], and Vermeer [5] [6]. Spectral-based automated thread counting also provides angle maps that make cusping assessment [7] and weft snake hunting [8] easier. Descriptions of the revelations possible from these new visualizations of canvas weave density and thread angle are provided in [9]. Technical description appears in [10] of the algorithms used in composing and comparing weave maps. References [1] C. R. Johnson, Jr., E. Hendriks, P. Noble, and M. Franken, Advances in Computer-Assisted Canvas Examination: Thread Counting Algorithms, 37th Annual Meeting of American Institute for Conservation of Historic and Artistic Works, Los Angeles, CA, May [2] C. R. Johnson, Jr., D. H. Johnson, N. Hamashima, H. S. Yang, and E. Hendriks, On the Utility of Spectral-Maximum-Based Automated Thread Counting from X-Rays of Paintings on Canvas, Studies in Conservation, vol. 56, pp , 2011.

4 Johnson and Sethares, Weave Map Report, August [3] L. van Tilborgh, T. Meedendorp, E. Hendriks, D. H. Johnson, C. R. Johnson, Jr., and R. G. Erdmann, Weave Matching and Dating of Van Gogh s Paintings: An Interdisciplinary Approach, The Burlington Magazine, vol. CLIV, pp , February [4] Pablo Pérez D Ors, C. R. Johnson, Jr., and D. H. Johnson, Velázquez in Fraga: a New Hypothesis about the Portraits of El Primo and Philip IV, The Burlington Magazine, vol. CLIV, pp , September [5] W. Liedtke, C. R. Johnson, Jr., and D. H. Johnson, Canvas Matches in Vermeer: A Case Study in the Computer Analysis of Fabric Supports, Metropolitan Museum Journal, vol. 47, pp , [6] C. R. Johnson, Jr. and W. A. Sethares, Canvas Weave Match Supports Designation of Vermeer s Geographer and Astronomer as a Pendant Pair, Journal of Historians of Netherlandish Art, vol. 9, issue 1, Winter DOI: /jhna [7] P. Noble, A. van Loon, C. R. Johnson, Jr., and D. H. Johnson, Technical Investigation of Rembrandt and/or Studio of Saul and David c from the Collection of the Mauritshuis, ICOM-CC 2011 Lisbon Triennial Conference, Lisbon, Portugal, September [8] C. R. Johnson, Jr., D. H. Johnson, I. Verslype, R. Lugtigheid, and R. G. Erdmann, Detecting Weft Snakes, Art Matters, vol. 5, pp , [9] D. H. Johnson, E. Hendriks, and C. R. Johnson, Jr., Interpreting Canvas Weave Matches, Art Matters, vol. 5, pp , [10] D. H. Johnson, C. R. Johnson, Jr., and R. G. Erdmann, Weave Analysis of Paintings on Canvas from Radiographs, Signal Processing (Special Issue on Image Processing for Art Investigation), vol. 93, pp , March Note: All of these references are available for download from

5 Johnson and Sethares, Weave Map Report, August Observations X-Radiograph: The impression of the canvas is visible throughout most of the x-radiograph of L33 in Figure 2. Average Thread Count: For L33 the average thread count (H x V) is x th/cm. These values are noted at the top of the images in the top row of Figure 3 along with the standard deviations of ±1.8 th/cm (H) and ±1.73 th/cm (V). The thread counts were computed in evaluation squares 0.5 cm on a side centered on a grid of points with 0.25 cm horizontal and vertical spacings. The histograms of the thread counts in each thread direction in the evaluation squares, as well as the histograms of the thread angles computed in the same evaluation squares, are plotted in Figure 4. Tight Count Matches: All of the weave matching pairs discovered so far among the canvases of paintings by Vermeer have had both thread counts within 1 th/cm of each other. Using this metric for the designation of a tight count match, L33 has five: L08 (The Glass of Wine, Gemäldegalerie Berlin), L09 (Girl Interrupted at Her Music, Frick Collection), L21 (Mistress and Maid, Frick Collection), L34 (A Young Woman Seated at a Virginal, National Gallery London), and L35 (The Guitar Player, Kenwood Museum). Weave Matches: Figure 9 is designed to assist in assessing if any of the tight count matches to L33 are also weave matches to L33. In Figure 9 all images are to the same scale, which is necessary for visual evaluation of potentially matching stripe patterns. The first two images in the second row are the horizontal thread density map of L08 and the vertical thread density map of L08 - rotated 90 degrees so the stripes are horizontal - with the same colorbar as used for the horizontal thread count for L33 on the left in the top row of Figure 9. These are to be placed on either the right or the left of the left image in the top row and moved up and down looking for a match of the stripe patterns. The images from the second row should be rotated 180 degrees as well in seeking matches in the striped patterns. Because the average horizontal thread count of L33 is less than the average vertical thread count of L08, the second image in the second row is lighter than the one on the left in the first row. Thus, only the horizontal thread density map of L08 need be compared to the

6 Johnson and Sethares, Weave Map Report, August horizontal thread density map of L33. No alignment offering a match of the striped patterns is apparent. A similar visual check is made with the third and fourth images in the second row of Figure 9 against the right image in the top row. The last two images in the second row are the vertical thread density map of L08 and the horizontal thread density map of L08 - rotated 90 degrees so the stripes are vertical - with the same colorbar as used for the vertical thread count for L33 on the right in the top row of Figure 9. These are to be placed either above or below the right image in the top row and moved right and left looking for a match of the vertical stripe patterns. Also, 180 degree rotations of the two rightmost images in the second row should also be considered for matching stripe patterns. Because the average vertical thread count of L33 is more than the average horizontal thread count of L08, the fourth image in the second row is da rkerthan the one on the right in the first row. Thus, only the vertilca thread density map of L08 need be compared to the vertical thread density map of L33. No alignment offering a match of the striped patterns is apparent. Of these four images in the second row, only one (or none, as in this case) can have a match with the corresponding images in the top row. This examination is repeated for the remaining rows containing the weave maps to be compared for the other tight count matches to L33. The match of the vertical thread density maps of L33 and L34 is illustrated in Figure 10 (and presented in [5]). Weft Snake Indicators: The horizontal thread angle map for L33 in Figure 7 displays two horizontal weft snake indicators: one approximately one-quarter of the painting s height from the bottom and another just above the middle. The one near the middle appears to coincide with the top edge of the center horizontal strainer bar. Deformation of the canvas at some point by pressure against the cross bar could be a cause for the wiggly bunch of threads visible in the x-radiograph. The lower weft snake indicator crosses the painting in the space between the bottom underside edge of the virginal and the blue seat of the chair. A corresponding wiggly bundle of threads appears in the x-radiograph. Thus, the horizontal threads are deemed the weft threads in L33. Cusping: From the thread angle maps of L33 cusping depth can be observed as greater than 5 cm on one side (bottom) and approximately 5 cm on the other three sides (top, left, and right).

7 Johnson and Sethares, Weave Map Report, August Acknowledgments The authors of this weave map report on one of Vermeer s paintings on canvas are grateful to the owners of Vermeer s paintings, all of whom gave us access to high resolution digitized x-radiographs of their Vermeers Walter Liedtke (Metropolitan Museum of Art) and Gregor Weber (Rijksmuseum) for their help in persuading the owners of paintings by Vermeer to grant us access to their x-radiographs Rob Erdmann (Rijksmuseum) for expertly assembling full-painting composite x-radiographs all of our research collaborators and thread-counting students over the past decade since the founding of TCAP: the Thread Count Automation Project ( tcap.html).

8 Johnson and Sethares, Weave Map Report, August Images Figure 1: A Young Woman Standing at a Virginal (L33) Note: All of the following images (Figures 2-10) are available on request as high resolution tiff or pdf files.

9 Johnson and Sethares, Weave Map Report, August Figure 2: X-Radiograph of L33

10 Johnson and Sethares, Weave Map Report, August horizontal thread density ( /- 1.8 threads/cm) vertical thread density ( / threads/cm) horizontal thread angles (+/ degrees) vertical thread angles (+/ degrees) Figure 3: Weave Maps of L33

11 Johnson and Sethares, Weave Map Report, August Figure 4: Histograms of Thread Count and Angle Computations for L33

12 Johnson and Sethares, Weave Map Report, August Figure 5: Horizontal Thread Density Map of L33

13 Johnson and Sethares, Weave Map Report, August Figure 6: Vertical Thread Density Map of L33

14 Johnson and Sethares, Weave Map Report, August Figure 7: Horizontal Thread Angle Map of L33

15 Johnson and Sethares, Weave Map Report, August Figure 8: Vertical Thread Angle Map of L33

16 Johnson and Sethares, Weave Map Report, August Figure 9: Tight Count Matches of L33

17 Johnson and Sethares, Weave Map Report, August Figure 10: Weave Match Between L33 Vertical Thread Density Map Rotated 180 Degrees (top) and L34 Vertical Thread Density Map (bottom)