PHOTOGRAPHY BY ULTRAVIOLET AND INFRARED 



599 



as the Eastman 40. If contrast is desired and some sensitivity can be sacrificed, plates 

 of the type of the Eastman 33 and Eastman Process and films like Eastman Commer- 

 cial and Eastman Process will be satisfactory. For fluorescent-light photography it 

 is necessary to use materials which are sensitive throughout the visible spectrum. All 

 panchromatic plates and films will be suitable, although usually fair contrast is desired, 

 and a material of the type of the Wratten Panchromatic Process or Wratten M plate 

 will be selected. 



Methods of Ultraviolet Photography. Reflected-iiltraviolet Method. — The subject 

 to be photographed is irradiated with ultraviolet from one or two sources and is placed 

 at the appropriate distance to give the evenness of illumination desired. To prevent 

 visible light from reaching the plate in the camera, an ultraviolet transmitting filter 



220v 

 D.C. 



Uvlarc 

 auxiliary 



^O^ 





Camera 



/ 



Fig. 1. — Diagram showing illuminant for reflected ultraviolet photography. 

 A — G. E 220-volt Horizontal Uviarc burner 

 S — Subject 



F — Ultraviolet transmitting filter, Corning "Ultra" glass. No. 586 



L — Ultraviolet absorbing filter, for photography of fluorescent effects, Wratten No. 2A 

 Exposure on Wratten Process Panchromatic Plates 



With filter L about 20 min. at //4.5. 



Without filter L about 1 min. at//16. 



must be used over the source or lens. In the former case the mercury- vapor lamp, or 

 other source, should be placed in a ventilated reflector which is completely covered 

 with a filter, such as the Corning Violet Ultra No. 586, and the operations must take 

 place in a totally darkened room. If the filter (Wratten No. 18A) is used on the lens, 

 the room may be lightened. There is a convenience in applying the filter to the source 

 rather than to the lens, since the same lighting unit can then be used for the fluorescent- 

 light method as well. If the arrangement shown in Fig. 1 is used, employing a single 

 General Electric Uviarc 220-volt horizontal burner with a Corning No. 586 filter over 

 the lamp and placing the lamp at 20 in. from the subject to be copied, the required 

 exposure will be of the order of 1 min. at //16 on the Wratten Panchromatic Process 

 plate. 



