locating surface is by design not a plane. Here the reference plane would be that plane containing the 
reference marks, for example the fiducial marks, while the image plane would be the surface of the film 
when brought into position for exposure. Laboratory calibration of the only camera type including a 
non-flat film locating surface is routinely carried out using a microflat glass plate for the 
determination of the lens distortion only. The radial image displacements caused by the non-flat film 
locating surface are then added to the lens distortion. The use of film and the magazine would result 
in the determination of the sum of lens distortion and radial displacements. 
As stated earlier, the use of film to make test exposures with the camera's magazine provides a 
direct laboratory simulation of the camera/magazine performance. Because of small defects in the film 
locating surface for any camera, such as variation from the intended shape of the film platen, 
irregularity of the film flattening system (vacuum) and variations of the focal plane frame, all 
magazines intended for use with a camera should be used to make film test exposures (Meier 1972). From 
these film exposures, contact diapositives that are measured for the calibration of the complete camera 
system are printed. Each film magazine would have an individual calibration report. 
Tables 1 to 6 show the results of three different calibrations of the same lens/camera system, 
first with flash plates (Tables 1 and 2), then using two different film magazines. To show the degree 
of precision for the determination of the lens dístortion of the lens/camera system five different sets 
of film exposure/glass diapositives were measured for three camera systems. The camera's film magazine 
was used to make test exposures of the collimator banks, and from these exposures contact glass 
diapositives were made for comparator measurements. The results are reported in Tables 7 to 9. As in 
Tables 1 through 6, the preliminary steps in the measurements are not described. The final values of 
the distortion along each of the four semi-diagonals and the averages of these four sets of values with 
the calibrated focal length is given. In no case did a semi-diagonal value depart from the five set 
average value by more than 2 micrometers. 
Since December 1, 1977, the U.S. Geological Survey has required that all magazine platens be 
equipped with an identification marker that will register a number on each frame of the original film 
at the time of exposure. The recording of the platen number ensures positive identification of the 
film magazine used. When an organization has more than one camera of the same manufacture, magazines 
can be interchanged inadvertently from the camera they were calibrated with. 
2.14 Presentation of Results 
2.14.1 The report should give at least the following data: 
2.14.2 The location of the principal point of autocollimation with respect to the fiducial 
centre.*) 
2.14.3 Calibrated principal distance, or calibrated focal length with criterion used to establish 
it. 
2.14.4 Curves (with plotting points shown) or a table of radial measured distortion, having as its 
origin the principal point of autocollimation as defined in section 2.2.3, along each of the 
four semi-diagonals and of the-average of these four sets of values.*) ; 
2.14.5 A statement of the maximum difference between radial-measured distortion at any field 
angle.*). 
2.14.6 A statement of the maximum value of tangential measured distortion based on the reference 
frame which makes this a minimum by making maximum values of opposite sign equal in magnitude. 
2.14.7 Distances between opposite pairs of fiducial marks, and the angle between the fiducial axes. 
The precise points involved should be thoroughly identified. 
2.14.8 The maximum departures (*) of the film locating surfaces from their correct shapes, or more 
complete information if required. 
2.14.9 If requested, a table giving the radial and tangential measured distortion at each point 
measured, and/or a statement of the orientation of the line through the principal point along 
which tangential measured distortion is calculated to be a maximum. 
2.14.10 A statement of the accuracies of all the information provided. 
Discussion 
At the present time, all camera calibration facilities report principal point and fiducial centre 
locations in a coordinate system, and some do so for the location of the fiducial marks. The methods 
used are all similar, with the exception of fiducial mark identification and coordinate origin. 
Fiducial centre, principal point of best symmetry and principal point of autocollimation are used as 
the origin. The coordinates routinely reported are 
  
*) If radial distortion relative to the principal point of best symmetry is also reported it should be 
clearly named and the position of the principal point of best symmetry should be given with respect 
to the fiducial centre. 
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