614 HANDBOOK OF PHOTOGRAPHY 



of the interiors of furnaces while they are operating, the detection of carbonaceous 

 matter in lubricating oils which have been used in internal-conabustion engines, and the 

 study of the porosity of tin plate. Infrared photography has proved of enormous 

 value in astronomy and spectrography. Hundreds of new lines have been recorded hi 

 the spectra of the elements, and much has been learned of the composition of the stars 

 and of the atmospheres of the planets. Photographs have been made through the 

 haze of nebulae, showing up stars normally invisible behind them, and large numbers 

 of new stars have been discovered by the infrared radiation which thej^ emit. It has 

 been found that the night sky is relatively much stronger in radiation of wavelength 

 8500 A. than in the violet and blue parts of the spectrum. In photomicrography 

 much use has been made of the infrared in the fields of entomology, cytology, histology, 

 embryology, and botany. In general, photomicrographs of deeply pigmented tissues 

 and the thicker microscopic sections and specimens show details of internal structure 

 when made by infrared which are not visible in ordinary photomicrographs. 



Special-effects Photography. — The dark skies, black shadows, and light grass and 

 trees, characteristic of outdoor infrared photographs, give them the appearance of 

 having been made by moonlight. Advantage is taken of this in the motion-picture 

 industry to make imitation moonlight photographs by operating in bright sunlight. 

 The method is superior to the use of underexposure of sunlit subjects, which has some- 

 times been proposed, and it has the advantages of not requiring the transportation of 

 lighting equipment outdoors at nighttime and of imposing no abnormal demands on 

 the players. Moonlight itself cannot be used because it would require exposures 

 which are unattainable in motion-picture practice. 



Works of Art. — Infrared photography has taken its place with chemical study and 

 X-ray and ultraviolet photography as an important means of determining the authen- 

 ticity of paintings. Pigments vary in the way in which they transmit and reflect the 

 infrared, even if they appear identical in color. Infrared photography can, therefore, 

 sometimes be of use in detecting the presence of overpainting and other alterations 

 and in distinguishing between an original and a later copy. Important factors are the 

 varnish and medium, which differ in their infrared transparency according to their 

 nature and age. Paintings which have so deteriorated due to darkening of the varnish 

 that detail can scarcely be seen may be revealed by infrared photography. Similarly, 

 photographs, daguerreotypes, engravings, drawings, maps, and other such documents 

 which have become badly discolored or faded by age or misuse have been successfully 

 photographed by infrared. 



Bibliography 



Ultraviolet 

 Periodicals: 



Bendikson, L.: A New Type of an Ultra-violet Light Source for Documentary Photography, Library J., 



69, 690-692 (1934). 



: A Cycle of Ultra-violet Light Sources for Various Uses, Library J. 61, 16-17 (1936). 



Btjttolph, L. J.: L^viarc Lamps and the Ultra-violet, General Electric Vapor Lamp Co., Hoboken, N. J., 



Engineering Dept. Bull. 105B. 

 General Electric Vapor Lamp Co. Various publications on Cooper-Hewatt lamps. 



Books: 



RoRiMEH, J. J.: "Ultra-violet Rays and Their Use in the Examination of Works of Art," Metropolitan 



Museum of Art, New York (1931). 

 Radley, J. A., and Grant, J.: " Fluorescence Analysis in Ultra-violet Light," 2d ed., Chapman (1935). 

 Grant, J.: "Books and Documents. Dating, Permanence and Preservation," Grafton & Co. (1937). 

 Beck, H.: " Photographic des Unsichtharen," Photokino-Verlag, Berlin (1936). 

 "Ultra-violet Photography." Eastman Kodak Co. Pamphlet, revised frequently. 



