C. Richard Johnson, Jr. Cornell University William A. Sethares University of Wisconsin - Madison

Transcription

1 1 WEAVE MAP REPORT The Art of Painting Johannes Vermeer c L26; inv Kunsthistorisches Museum C. Richard Johnson, Jr. Cornell University 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 The Art of Painting (L26) 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. comments on observed cusping and weft snakes Observations: The average thread density of The Art of Painting is (H x V) is x th/cm. The Art of Painting has cusping of depth greater than 5 cm on all four sides. The Art of Painting has no close count matches, and therefore no weave matches, among Vermeer s other paintings on canvas. The horizontal thread angle map of The Art of Painting displays one weft snake indicator.

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 L26 in Figure 2. In a few places, such as highlights on the chandelier and the bright wall between the curtain in the left foreground and the map on the wall, the paint is sufficiently opaque to the applied x-ray intensity to make manual counting quite a challenge in those locations. Average Thread Count: For L26 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 ±1.17 th/cm (H) and ±1.55 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, L26 has none. Weave Matches: With no close count matches, L26 has no weave matches among Vermeer s paintings on canvas. Weft Snake Indicators: The horizontal thread angle map for L26 in Figure 7 displays one weft snake indicator approximately one-third of the painting height from the top edge. This weft snake indicator corresponds to a wiggly bunch of horizontal threads visible in the x-radiograph. Thus, the horiizontal threads are deemed the weft threads in L26. This is in agreement with the selvedge remaining on the left edge of the painting. Cusping: From the thread angle maps of L26 cusping can be observed as greater than 5 cm on all four sides.

6 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).

7 Johnson and Sethares, Weave Map Report, August Images Figure 1: The Art of Painting (L26) Note: All of the following images (Figures 2-8) are available on request as high resolution tiff or pdf files.

8 Johnson and Sethares, Weave Map Report, August Figure 2: X-Radiograph of L26

9 Johnson and Sethares, Weave Map Report, August 2017 horizontal thread density ( / threads/cm) vertical thread density ( / threads/cm) horizontal thread angles (+/ degrees) vertical thread angles (+/ degrees) Figure 3: Weave Maps of L26 9

10 Johnson and Sethares, Weave Map Report, August Figure 4: Histograms of Thread Count and Angle Computations for L26

11 Johnson and Sethares, Weave Map Report, August Figure 5: Horizontal Thread Density Map of L26

12 Johnson and Sethares, Weave Map Report, August Figure 6: Vertical Thread Density Map of L26

13 Johnson and Sethares, Weave Map Report, August Figure 7: Horizontal Thread Angle Map of L26

14 Johnson and Sethares, Weave Map Report, August Figure 8: Vertical Thread Angle Map of L26