Technical examinations of images, called imaging techniques, provide information in the form of visuals. Photography is the simplest imaging technique. Its use is very important before any conservation work starts, and it also provides invaluable information during and after the completion of restoration and maintenance work. A key advantage of imaging techniques is that a work can by examined in a non-invasive manner. These techniques use both visible (visible range) and invisible radiation waves. They are able to take advantage of the full electromagnetic spectrum. The types of invisible radiation used in the study of art are ultraviolet radiation (that type we safeguard against when under sunlight), infrared (a type of radiation often used as a heat source), and X-ray (which is often used for medical imaging). Some of these types of radiation have wavelengths that can be "seen" and recorded by a multispectral imaging camera. The information obtained every time depends on the camera and light bulbs used as well a the work being examined. Imaging techniques can provide information about the construction of a work, and other pertinent information, like whether a work has previously restored sections or whether a painting has any underpainting, a painting invisible to the naked eye which is located below the visible painted surface. The results can be especially impressive when examining works that have invisible painted layers and underpainting!