Underdrawings of paintings imaged through infrared photography or IR reflectogra phy with a vidicon is a tehnique of major importance to numerous art historians. Unfortunately for e-mail it's too large of a subject to discuss here, however, you might try to contact several individuals who are well know for their use of this tool. Prof. Molly Fairies at the Indiana University (812-339-8208; Maryanne Ainsworth at the Metropolitan Museum of Art; J.R.J. Van Asperen de Boer, Groningen Univers ity, Netherlands; Rachel Billlinge, The National Gallery of Art, UK.