Exposure of Underdrawings in Oil Paintings Through IR Analysis Chad B. Weiner Dr. Jon Arney May 8, 1998
Review - Underdrawings zPreparatory drawings applied directly to a ground and then covered by the oil painting. zMedia used ymostly charcoal ypencil ychalk
Review - IR Reflectography zInfrared radiation passes through the paint layer while being reflected by the charcoal substrate.
Aims of Research zTo improve current IR underdrawing analysis techniques (Reflectography) using image processing methods. zTo develop a means of removing the paint layer from the underdrawing using an equation derived from Kubelka-Munk theory.
Research Methodology zSamples - charcoal drawings sketched on a canvas & painted over by flake-white oil-based paint. zVIS images captured using a COHU camera. zIR images captured using a COHU camera covered by an Infrared filter.
Programming zVisual Basic Program yK, n -> variables
Results Image Subtraction K=3.0, n = 1.3
Results IR K=3.0, n = 1.3
Future Research Possibilities zIncorporate Kubelka-Munk Theory yConvert Grayscale Values from camera output into Reflectances yDetermine the Absorption Coefficient ySolve for the Ground Reflectance (Underdrawing)
Conclusions zUnable to derive an equation from Kubelka-Munk Theory zCompleted research provides enough evidence that it is possible to remove the paint layer and other artifacts from an underdrawing