(678) 
first class photo equipment. Fast operation cameras of the polaroid type should 
also be included in the equipment, and, preferably, even stereo-cameras intend- 
ed for measuring purposes. 
Use. 
Detailed reconnaissance 
is carried out by specially 
trained photographers, who 
have sufficient knowledge of 
photo technique to be able to 
make full use of the scope 
offered by the equipment. In 
fig. 10 a reconnaissance pho- 
tographer is shown at work 
in winter time. 
Detailed photo  recon- 
naissance Is carried out on the 
front lines of enemy defences 
with the intention of ascer- 
taining what kind of fortifi- 
cations he has erected. Stereo 
photos are, if possible, taken 
with both panchromatic and 
infrared-sensitized materials, 
in combination with suitable 
Fig. 10. A reconnaissace photographer at work in filters. This form of recon- 
winter time. naissance on emplacements is 
in many cases only slightly 
superior to efficiently carried out observations with field glasses. In summer 
time, however one can sometimes achieve good results with infrared films and a 
black filter and also with camouflage penetrating films, which under certain 
conditions, can detect camouflage works which cannot be seen with the naked 
eye. 
Through continual photographic observation of one and the same area of 
terrain, and comparative interpretation of the photos taken, one gets the possi- 
bility of ascertaining day-by-day changes in the enemy sector which the ob- 
server would perhaps not notice (see figs. 11-12). Newly erected emplacements, 
fortifications and new camouflage material etc. can give useful intelligence 
about the enemy activity at that time. 
In winter time, detailed photo reconnaissance has not such great possibili- 
ties, especially on cloudy days, when the snow has few shades of colour and 
there are no shadows. Under such conditions, the exposure should be carefully 
chosen according to the reflex light of the snow, although the other parts of the 
negative will then be under-exposed. 
At night it is possible to ascertain with considerable accuracy the positions 
of guns in action (see fig. 13). In this case, the photos are taken with several 
cameras set up along a base line, and directed on the terrain in question in such 
a way that stereographic picture-reading at each point is possible. After dark, 
  
  
  
    
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
    
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
  
  
  
  
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