(205) 
posal), contrast rendition, and tangential distortion. All these terms are simply 
omitted in the proposal. 
Some of these omissions will probably be acceptable to American photo- 
grammetrists if they recognize the fact that the determination of the equivalent 
focal length and of the “American” principal point is not necessarily of uni 
versal technical importance and interest. 
Some omissions can probably be easily rectified by permitting the use of 
the alternate term (contrast rendition, for example). 
Some omissions, however, will require more profound discussion of the 
supporting argumentation. Thus the argumentation for restricting the term 
“distortion” to its theoretical content should be critically evaluated, because 
it is contrary to the prevailing American and European practice. If such a 
rather artificial argumentation is accepted, then, for example, a new term 
should be invented also for the measured spherical aberration, because imper 
fections of manufacture may destroy its perfect symmetry about the optical 
axis. 
Terminology frequently proves to be a serious stumbling block in stand 
ardization undertakings. Let us hope that problems of terminonlogy will be 
easily resolved by Commission I, and that its proposal will be evaluated with 
the spirit of compromise and international goodwill, which are the basic con 
ditions for the success of our undertaking. 
Mr. F. L. Corten: 
Mr. Chairman, ladies and gentlemen. At the International Congress of 
Photogrammetry in 1948, Captain Reading stated that we were badly in need 
of international standardization of calibrating and measuring the performance 
of photogrammetric cameras. The result of his initiative and of the work done 
by many of those present is now lying before us. 
I shall confine my remarks on these proposals to a few points. 
With section 1, dealing with the measurement of resolution and photo 
graphic performance, I can agree for the time being. 
Section 2 deals with the calibration which should preferably be done 
photographically, whereas a visual goniometer is also permissible. The philo 
sophy underlying the photographic method is a very sound one and it is gene 
rally agreed that in principle the photographic method is to be preferred. One 
point remains to be established in the near future: what accuracy can be 
reached, in other words; what is the statistical and chronological spread in the 
results of the photographic method, if a larger number of identical calibrations 
is carried out? In view of the recent developments in optics and in mechanics, 
both in cameras and in plotting apparatus, we should be able to arrive at a 
reliability of ± 1 micron, that is less than one ten thousandth of an inch! This 
is a very rigid demand, but it is clear that the claims to be set for the calibra 
tion should be at least as exacting as the claims set for modern precision survey 
cameras. It is true that Item 2.14.10 requires a statement of the accuracies of 
all information provided, but what the photographic method is capable of in 
this respect has not yet been investigated systematically. Therefore, it would 
be a valuable contribution if such an investigation could be made as a coping 
stone for the calibration of survey cameras. There is an additional remark on 
section 2 in general: The establishment of a complete set of fundamental pho-