page_title: Infrared
section_title: Art conservation and analysis
hierarchical_section_title: Infrared / Applications / Art conservation and analysis
caption_attribution_description: English: Infrared reflectograms of Mona Lisa by Leonardo da Vinci. Français&#160;: Réflectographie infrarouge de la Joconde par Léonard de Vinci.
context_page_description: Infrared, sometimes called infrared light, is electromagnetic radiation with wavelengths longer than those of visible light. It is therefore generally invisible to the human eye, although IR at wavelengths up to 1050 nanometers s from specially pulsed lasers can be seen by humans under certain conditions. IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers, to 1 millimeter. Most of the thermal radiation emitted by objects near room temperature is infrared. As with all EMR, IR carries radiant energy and behaves both like a wave and like its quantum particle, the photon.
  Infrared radiation was discovered in 1800 by astronomer Sir William Herschel, who discovered a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. Slightly more than half of the total energy from the Sun was eventually found to arrive on Earth in the form of infrared. The balance between absorbed and emitted infrared radiation has a critical effect on Earth's climate.
  Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements.
context_section_description: Infrared reflectography can be applied to paintings to reveal underlying layers in a non-destructive manner, in particular the artist's underdrawing or outline drawn as a guide.  Art conservators use the technique to examine how the visible layers of paint differ from the underdrawing or layers in between (such alterations are called pentimenti when made by the original artist). This is very useful information in deciding whether a painting is the prime version by the original artist or a copy, and whether it has been altered by over-enthusiastic restoration work. In general, the more pentimenti, the more likely a painting is to be the prime version. It also gives useful insights into working practices. Reflectography often reveals the artist's use of carbon black, which shows up well in reflectograms, as long as it has not also been used in the ground underlying the whole painting.
  Recent progress in the design of infrared-sensitive cameras makes it possible to discover and depict not only underpaintings and pentimenti, but entire paintings that were later overpainted by the artist. Notable examples are Picasso's Woman Ironing and Blue Room, where in both cases a portrait of a man has been made visible under the painting as it is known today.
  Similar uses of infrared are made by conservators and scientists on various types of objects, especially very old written documents such as the Dead Sea Scrolls, the Roman works in the Villa of the Papyri, and the Silk Road texts found in the Dunhuang Caves. Carbon black used in ink can show up extremely well.
caption: An infrared reflectogram of Mona Lisa by Leonardo da Vinci
exif: {"Image Tag 0x000B": "Windows Photo Editor 10.0.10011.16384", "Image ImageDescription": "", "Image Make": "Canon", "Image Model": "Canon PowerShot G15", "Image Orientation": "Horizontal (normal)", "Image XResolution": "180", "Image YResolution": "180", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Windows Photo Editor 10.0.10011.16384", "Image DateTime": "2019:12:17 16:58:18", "Image Artist": "Tangopaso", "Image YCbCrPositioning": "Co-sited", "Image Copyright": "", "Image ExifOffset": "2446", "GPS GPSVersionID": "[2, 3, 0, 0]", "Image GPSInfo": "9250", "Image Padding": "[]", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "96", "Thumbnail YResolution": "96", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "9364", "Thumbnail JPEGInterchangeFormatLength": "8302", "EXIF ExposureTime": "1/30", "EXIF FNumber": "2", "EXIF ISOSpeedRatings": "800", "EXIF SensitivityType": "Standard Output Sensitivity and Recommended Exposure Index", "EXIF ExifVersion": "0230", "EXIF DateTimeOriginal": "2019:12:11 10:01:22", "EXIF DateTimeDigitized": "2019:12:11 10:01:22", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "157/32", "EXIF ApertureValue": "2", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "2", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "1353/200", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2816", "EXIF ExifImageLength": "2112", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "Interoperability RelatedImageWidth": "2816", "Interoperability RelatedImageLength": "2112", "EXIF InteroperabilityOffset": "9180", "EXIF FocalPlaneXResolution": "2816000/293", "EXIF FocalPlaneYResolution": "9600", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF SceneCaptureType": "Standard", "EXIF CameraOwnerName": "", "EXIF Padding": "[]", "EXIF OffsetSchema": "4256"}