= 
A 
  
(5) 
FIG. 17 DIAGRAM OF LEFT AND RIGHT HEAD FILMS SHOWING THE LOCATIONS OF 
THE POINTS IN THE UPPER AND LOWER ENDS OF THE STUDS OF THE 
PRINCIPAL POINT LOCATOR. IN (A), THE POINTS IN THE RIGHT HEAD 
FILM HAVE BEEN TRANSFERRED TO THE LEFT HEAD FILM TO SHOW THE 
PARALLAX DISPLACEMENTS OF THE POINTS 
Exposure 
  
  
Station 
  
uae 
  
  
  
  
  
Datum— 
  
  
FIG. 18 DETERMINATION OF c AND H FROM MEASUREMENTS OF PHOTOGRAPHIC 
ENLARGEMENTS