608 



HANDBOOK OF PHOTOGRAPHY 



Films for Aerial Photography: 



Agfa Infra-red Aero Film 



Eastman Infra-red Aero Film 

 All the foregoing materials are sensitive in the near infrared in a band somewhere 

 between 6500 and 8500 A. They have the general characteristics of fast negative 

 emulsions with the exception of the Eastman Infra-red Process plate, which is a 

 process-type material. 



Methods of Infrared Photography. — For general infrared landscape photography a 

 plate camera or a miniature camera using 35-mm. film is used with the Wratten 

 No. 25 or a similar filter on the lens. The plates or films sensitive in the region 

 between 6500 and 8500 A. are the most satisfactory. Correction for infrared focus 

 should be made if necessary. Exposure meters which measure visible light are not 

 reUable, and the manufacturer's exposure guides should be used. Typical exposure 

 for a sunlit open landscape in summer is ^5 sec. at//5.6 through the Wratten No. 25 

 filter using the Eastman Infra-red Sensitive plate or Kodak Infra-red film type 



Background 



Subject 



Koc/aflecfor L-1 

 Level iv/M camera 



Kodaflecior L-2 

 Level with camera 



Background 



Subjeci 



Phol-of/ood 

 lamfi 



To current 

 supply 



Kodaf lector L-1 ^^ Koda fleeter L-2 

 Level with camera l - y ' .. ' ,'.'A Level with cam.era 



Camera 



To current supply 



A B 



Fig. a. — Typical arrangement of lights for infrared photography. The diagram at A shows 



the use of photoflood lamps, whereas B shows a method of using photoflash lamps. 



IR-135. In practice it appears that on dull days the increase in exposure for infrared 

 materials is about double that which would be required for panchromatic plates and 

 films. 



For photography indoors using artificial light, two arrangements are possible. In 

 one case, the lights are used open, with a filter on the lens of the camera. In the other, 

 it is desired to make pictures in total darkness, and in this case filters must be used over 

 the lamps to absorb all visible light and to transmit the infrared freely; no filter is 

 necessary on the lens. For infrared portraits in the lighted studio, the normal studio 

 lamps are employed, but the lighting should be rather flat, because it is rarelj'' required 

 to produce modeling in the subject, but merely differences in reflection and trans- 

 mission of the skin. This is particularly so with medical subjects. In infrared 

 copying of documents and photography of general objects, the normal arrangement of 

 flat lighting is used. Typical arrangements of the lights are shown in Fig. 4. In 

 arrangement A two pairs of photoflood lamps or 500-watt projector type lamps are 

 used in reflectors arranged symmetrically to the subject at 45°. If a single photoflash 

 lamp is employed, it should be placed as near the camera axis as possible. Better 

 results are obtained by using two photoflash lamps as shown in arrangement B. They 

 are fired simidtaneously by an appropriate switch wired to the two lamps. A single 



