The use of technology has always been part of an appraisers arsenal when evaluating property. The use of technology can assist the appraiser in identification as well as report preparation. Professor Charles Falco, an optics professor at the University of Arizona wrote an interesting article about photographing art with a digital camera that was converted to shoot in infra red.The Journal is published by the Foundation for Appraisal Education, and proceeds from journal sales support the educational initiatives and scholarships of the foundation. The 2011 edition is the fourth annual published.
The article is very interesting as well as the images which reveal numerous details of art when photographed using infra red. As professional appraisers, we should be aware of what new technologies are not only being used in museum conservations labs, as well as what is available to the appraiser for field use, such as the converted IR cameras Charles Falco writes about.
Charles Falco writes in the Journal of Advanced Appraisal Studies
The IR-modified camera discussed here does not cover the full range of wavelengths possible with a specialized camera that uses a sensor other than silicon,8 and does not produce the ideal quality that would be possible if a painting were examined under conditions of uniform lighting. However, as the examples in this manuscript show, its high resolution, low cost, portability, and ease of use by non-specialists represents a significant advance over what has been possible prior to this. Such a modified commercial digital camera for the first time makes it possible for any museum to capture high resolution IR reflectograms of their entire collection in situ without significant expenditure of staff time, and without disrupting the exhibition requirements of the institution. In cases where analysis of an IR reflectogram revealed significant features, the new information would help curators decide if certain paintings warranted further detailed study by other scientific techniques.
The 1100 nm upper limit of sensitivity means some features in some paintings cannot be imaged with this camera, because not all pigments are semi-transparent in this wavelength range. However, only a small percentage of paintings in museums ever have been studied in the IR,6 which means that currently no information at all is known about them from this technique. As the Lotto example illustrates, important information that otherwise simply would not be known can be revealed in IR reflectograms acquired in situ with this portable imaging system, at an average time of less than a few minutes per painting.19
Conclusions
An inexpensive, highly portable, imaging system based on a modified digital camera has been developed that allows non-specialists to obtain high resolution IR reflectograms of works of art in situ. The capabilities of this system were illustrated with several examples, including one that confirmed and extended conclusions about how optical projections were used by a specific artist in the 16th century.
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