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Exposure of Underdrawings in Oil Paintings Through IR Analysis

Exposure of Underdrawings in Oil Paintings Through IR Analysis. Chad B. Weiner Dr. Jon Arney May 8, 1998. Review - Underdrawings. Preparatory drawings applied directly to a ground and then covered by the oil painting. Media used mostly charcoal pencil chalk. Review - IR Reflectography.

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Exposure of Underdrawings in Oil Paintings Through IR Analysis

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  1. Exposure of Underdrawings in Oil Paintings ThroughIR Analysis Chad B. Weiner Dr. Jon Arney May 8, 1998

  2. Review - Underdrawings • Preparatory drawings applied directly to a ground and then covered by the oil painting. • Media used • mostly charcoal • pencil • chalk

  3. Review - IR Reflectography • Infrared radiation passes through the paint layer while being reflected by the charcoal substrate.

  4. Aims of Research • To improve current IR underdrawing analysis techniques (Reflectography) using image processing methods. • To develop a means of removing the paint layer from the underdrawing using an equation derived from Kubelka-Munk theory.

  5. Research Methodology • Samples - charcoal drawings sketched on a canvas & painted over by flake-white oil-based paint. • VIS images captured using a COHU camera. • IR images captured using a COHU camera covered by an Infrared filter.

  6. Data Analysis • Preliminary analysis - IMLAB software. • UD(i, j) = VIS(i, j) - IR(i, j)

  7. Data Analysis IR Image Subtraction

  8. Programming • Visual Basic Program • K, n -> variables

  9. Results Image Subtraction K=3.0 , n = 1.3

  10. Results IR K=3.0 , n = 1.3

  11. Future Research Possibilities • Incorporate Kubelka-Munk Theory • Convert Grayscale Values from camera output into Reflectances • Determine the Absorption Coefficient • Solve for the Ground Reflectance (Underdrawing)

  12. Conclusions • Unable to derive an equation from Kubelka-Munk Theory • Completed research provides enough evidence that it is possible to remove the paint layer and other artifacts from an underdrawing

  13. The End

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