Infrared Photography (IR)
Photographic set up
Check out the Infrared Photography Lenses Database
Applications in Art examination
IR versus IRR
Infrared Reflectography (IRR) is imaging infrared over 1100 nm and up to 1700 nm or 2500 nm (depending on the imaging detector type). A full spectrum digital camera can record light until about 1100 nm while an InGaAs camera until about 1700 nm.
Pigments that are MORE transparent with an InGaAs camera
Some pigments become considerably more transparent at longer infrared wavelengths (i.e. using an InGaAs camera). This statement is true for some historical pigments, not for all of them. And in many cases the increase in transmittance is negligible.
Azurite, the affordable blue used in pre-industrial age European art, is an example of those pigments whose transmittance increases at longer infrared wavelength (IRR).
Pigments that have the SAME transmittance in digital full spectrum camera (IR) and InGaAs camera (IRR)
Vermilion is among the most used red historical pigments. It is common in oil and tempera paintings. The InGaAs camera does not increase its transparency, at all.
Pigments that are LESS transparent with the InGaAs camera
Cobalt blue was loved by Vincent van Gogh who said to his brother Teo, ‘Cobalt blue is a divine colour and there is nothing so beautiful for putting atmosphere around things…”. Even if it seems counter intuitive, cobalt blue, cobalt green and smalt, are less transparent in the IRR (InGaAs) than in IR.
|Publications on Infrared Photography (IR)|
|A. Cosentino "Infrared Technical Photography for Art Examination” e-Preservation Science, 13, 1-6, 2016.|
|A. Cosentino “Identification of pigments by multispectral imaging a flowchart method” Heritage Science, 2:8, 2014.|
|A. Cosentino "Effects of Different Binders on Technical Photography and Infrared Reflectography of 54 Historical Pigments” International Journal of Conservation Science, 6 (3), 287-298, 2015.|