The most common application of Infrared Photography is to show preparatory under-drawings, composition variations and difficult to read inscriptions.
An Aid for the Conservator-Restorer: Infrared Photography

The most common application of Infrared Photography is to show preparatory under-drawings, composition variations and difficult to read inscriptions.
Inpainting, retouching and over-painting are terms commonly used in the conservation - restoration field. On occasion they are used interchangeably, but there are subtle differences that should be clarified.