Jon Harman, Ph.D.

Jon Harmon

Jon Harman has spent over twenty years pursuing rock art as a serious hobby.  He is a member of the Bay Area Rock Art Research Association (BARARA), the Society for California Archaeology and the American Rock Art Research Association (ARARA).  He has traveled throughout the United States as well as to Mexico, North Africa and France in search of petroglyph and pictograph sites.

Jon earned a Bachelor of Arts in Mathematics in 1972 from the University of Wisconsin in Madison and a Ph.D. in Mathematics in 1980 from the University of California in Berkeley.  With this background, he enjoyed a lengthy career in the field of medical imaging.  He worked for a CT manufacturer and an ophthalmology device manufacturer, specializing in the design of algorithms used in creating medical images and in analyzing structures in the images.

A suggestion from Robert Mark in November 2004 led to Jon’s implementing the decorrelation stretch scientific algorithm in a computer program that would assist rock art researchers.  Jon then combined his career and hobby to create DStretch, an image enhancement program to be used specifically with digital photographs of pictographs.  It is a plug-in for Image J, which is a public domain image processing program developed at the National Institute of Health by Wayne Rasband.

See D-Stretch example images below.

D stretch

DStretch was introduced to the public in March 2005 at a meeting of the Society of California Archaeology in Sacramento.  It has rapidly gained widespread recognition and acceptance as an invaluable research tool.  Because DStretch requires a color difference, it works significantly better on pictographs, particularly those containing faint red, yellow and/or black.  It enables the user to examine a photograph of a pictograph under eight different color spaces and see elements not visible in the original image.

Pictograph panels previously dismissed as insignificant or impossible to see can now be examined in a new light.  Some particularly dramatic examples are from Great Basin National Park, Nevada; Pahranagat National Wildlife Refuge, Nevada; Kachina Cave, Nevada; Buckhorn Wash, Utah; Head of Sinbad, Utah; Chumash and Yokuts pictographs in central California; and the Great Mural Paintings of Baja California.

Since the advent of DStretch, rock art researchers and enthusiasts have been returning to sites with their digital cameras and re-photographing pictographs.  Their results have been both amazing and revealing.

Jon has presented papers on the use of DStretch at meetings of the Museum of Man in San Diego , the Society for California Archaeology, ARARA, the Nevada Rock Art Foundation, the Nevada Archaeological Association, the Bi National Meeting of Balances and Perspectives on the Anthropology and History of Baja California and the Sociedad Mexicana de Antropologia.