Young Lady Reading a Letter at an Open Window Johannes Vermeer c L05 / Gal.-Nr Staatliche Kunstsammlungen Dresden

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1 1 WEAVE MAP REPORT Young Lady Reading a Letter at an Open Window Johannes Vermeer c L05 / Gal.-Nr Staatliche Kunstsammlungen Dresden 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 Young Lady Reading a Letter at an Open Window (L05) 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. histograms of vertical and horizontal thread counts 5. vertical thread angle map 6. horizontal thread angle map 7. a listing of all close count matches (wthin ±1 th/cm in both directions) among Vermeer s 34 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. comments on observed cusping and weft snakes Observations: The average thread density of Young Lady Reading a Letter at an Open Window (H x V) is x th/cm. The Young Lady Reading a Letter at an Open Window has cusping on all four sides. The Young Lady Reading a Letter at an Open Window has five close count matches but no apparent weave matches among Vermeer s other paintings on canvas. The Young Lady Reading a Letter at an Open Window has two horizontal weft snake indicators.

3 Johnson and Sethares, Weave Map Report, August Background 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 (smaller compared to smaller and larger coompared to larger) are too diffferent, 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 assessement [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 , [3] L. van Tilborgh, T. Meedendorp, E. Hendriks, D. H. Johnson, C. R. Johnson, Jr., and R. G. Erdmann, Weave Matching and Dat-

4 Johnson and Sethares, Weave Map Report, August ing 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: From Figure 2, it appears that four separate x-ray films have been sliced to build a composite. Without overlap between the consituent x-radiographs a precise stitched composite is impossible to assemble. The resulting composite in Figure 2 has a horizontal cut in the strainer bar and a vertical cut through the young lady s head. Average Thread Count: 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 ± 1.27 th/cm (H) and ± 1.43 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 matches 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, L05 has six: L15 (The Music Lesson, The Royal Collection, Windsor Castle), L20 (A Lady Writing, National Gallery of Art - DC), L27 (The Goegrapher, Städelsches Kunstinstitut, Frankfurt am Main), L28 (The Astronomer, Musée du Louvre) L30 (The Love Letter, Rijksmuseum), and L32 (Allegory of the Catholic Faith, Metropolitan Museum of Art). Weave Matches: Figure 9 is designed to assist in assessing if any of the six count matches is a weave match to L05. 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 L15 and the vertical thread density map of L15 - rotated 90 degrees so the stripes are horizontal - with the same colorbar as used for the horizontal thread count for L05 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 around looking for a match of the stripe patterns. Because the average vertical thread count in L15 is much higher than the average horizontal thread count in L05, the second

6 Johnson and Sethares, Weave Map Report, August image in the second row is quite light. So, only the horizontal thread density map of L15 need be compared to the horizontal thread density map of L05. 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 L15 and the horizontal thread density map of L15 - rotated 90 degrees so the stripes are vertical - with the same colorbar as used for the vertical thread count for L05 on the right in the top row of Figure 9. These are to be placed either above or below of the right image in the top row and moved around looking for a match of the vertical stripe patterns. Because the average horizontal thread count in L15 is much lower than the average vertical thread count in L05, the second image in the second row is quite dark. So, only the vertical thread density map of L1 need be compared to the horizontal thread density map of L05. Of these four images in the second row, only one (or none) can have a match. In this case none appear to have a match. The same conclusion is drawn about L20, L27, L28, L30, and L32 after repeating the similar comparisons with the third through the seventh rows and the first row in Figure 9. Weft Snake Indicators: Two horizontal weft snake indicators cross the horizontal thread angle map in Figure 7 about 25 cm down from the top edge and about 20 cm up from the bottom edge. The top weft snake indicator crosses the painting at the top of the open window frame. A close-up look at Figure 2 reveals a wiggly bunch of threads crossing the painting, i.e. a weft snake. The lower weft snake indicator crosses the painting at the level of the lower edge of the reader s left sleeve. The wiggly weft snake at this location is milder than the one in the top third of the painting. These weft snakes indicate that the horizontal thread direction is the weft. Cusping: The cusping is greater than 5cm in depth on all four sides.

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: Young Lady Reading a Letter at an Open Window (L05) Note: All of the following images (Figures 2-9) are available on request as high resolution tiff or pdf files.

9 Johnson and Sethares, Weave Map Report, August Figure 2: X-Radiograph of L05

10 Johnson and Sethares, Weave Map Report, August horizontal thread density ( / threads/cm) vertical thread density ( / threads/cm) horizontal thread angles (+/ degrees) vertical thread angles (+/ degrees) Figure 3: Weave Maps of L05

11 Johnson and Sethares, Weave Map Report, August Figure 4: Histograms of Thread Count and Angle Computations for L05

12 Johnson and Sethares, Weave Map Report, August Figure 5: Horizontal Thread Density Map of L05

13 Johnson and Sethares, Weave Map Report, August Figure 6: Vertical Thread Density Map of L05

14 Johnson and Sethares, Weave Map Report, August Figure 7: Horizontal Thread Angle Map of L05

15 Johnson and Sethares, Weave Map Report, August Figure 8: Vertical Thread Angle Map of L05

16 Johnson and Sethares, Weave Map Report, August Figure 9: Tight Count Matches of L05