Scientific analyses of paintings running for expertise or restoration purposes are using different optical technologies which each of them are supplying different information about the constitution and evolution of the painting.
The use of a near infrared camera allows passing through the different layers of a painting which isn’t the case for visible light. The infrared reflectography is independent form the painting’s support and is the most suitable method for the visualization of underdrawings. Infrared imaging can contribute to the study of painting techniques as well as to the recording of the extent of later retouching. The method also allows visualizing preparatory drawings, repentirs, potential surpaints or hidden invisible signatures.

The new generation of high resolution InGaAs near infrared cameras with 640 x 512 pixels helps to improve the scientific analyses by using better infrared reflectography images.
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Original	near infrared camera

reflectography detail of the painting Eliézer et Rébecca from Jan Swart (1495-1560), oil on wood. 
Musée national d’histoire et d’art Luxembourg