a. should no particular accuracy characteristics be required by the work in question, the € 
unaccuracy of the principal point within few hundreds of millimetres does not comprimise the 
results of the work itself. 
b. Should the work to be carried out require the maximum accuracy, the principal point position 
corresponding to each position of the lens may be established during the camera calibration and 
the obtained values recorded on the calibration certificate, 
At last as the principal point shifting is caused by the mechanical working of the different 
units moving the lens, it should be possible to reduce, through a different and highly expensive 
operation, theis shifting to a few microns i. e. to a negligible quantity yet for the highest accuracy 
work. This method was not followed in the practical realization of the camera as it is not essential 
in the most applications of the non topographic photogrammetry. 
  
© € 
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