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well as the user, undoubtedly an urgent necessity. Therefore various testing 
methods have been developed in the course of the last years. 
In order to understand clearly a testing result, it is necessary to have an 
exact knowledge of the details of the testing programme. The endeavours of 
American and European photogrammetrists has been directed, since the last 
Congress in Holland, thanks to the initiative and suggestions of Captain 
Reading, towards the creation of standardized testing methods in order to 
facilitate the judgment of aerial cameras. In the past four years the coopera 
tion of the American and European scientists under the management of Dr. 
Howlett has resulted in a repeatedly improved proposal for this test. The 
proposal is now before us for discussion. We have the possibility to accept it as 
such, to refuse it, or eventually to make new changes. I personally am of the 
opinion that the proposal represents a good working base and approaches more 
or less the goal which we have set four years ago. In order to come out of the 
status of discussion, I think that we should accept it without any additional 
changes and have it in force until the next Congress meets. 
At the same time I would suggest that besides the testing laboratories of 
the manufacturers, there should be at least two neutral testing organizations, 
one on the American and one on the European continent, where standard tests 
can be executed. These testing stations should be equipped with the most reli 
able and precise instruments in order to test all kinds of aerial cameras. In 
order to ensure the relative evenness of the tests, these central organizations 
should have one to two normal objectives of any make which would permit 
them to control at all times the operations and the procedures of the testings. 
I think that in Europe, for instance, the International Training Centre for 
Photogrammetry in Delft, which is under the management of Professor Scher- 
merhorn, could take over this task. 
The fact that I recommend the acceptance of the proposal which is before 
you, rests on the experience which I have had with a similar testing method 
applied in the manufacture of the objectives of the firm Henry Wild. In the 
physical laboratories of Wild, each objective lens which is manufactured is 
being tested, not only on its geometrical properties, but also on the picture 
quality such as foreseen in the proposal. The manufacturing tolerances are 
being established in accordance with the proposed test. I can state that we are 
very satisfied with this method. It guarantees us a very even manufacturing 
quality. In the testing, the geometrical properties of the objective lens are not 
in the first place of the discussion. It is tolerances in accordance with the pur 
pose of the camera. The certainly in obtaining the results is very high, and the 
results can be repeated at any time. 
When measuring the resolving power, dispersions of about ± 10% cannot 
be avoided. But within this scope the resolving power is as a rule very well 
defined. Mostly there is only a dispersion of single measuring points, and the 
smoothed curves are almost the same in form and height. Also small manu 
facturing errors in the serial manufacture can be easily detected and afterwards 
corrected or eliminated. 
The text of the proposal can undoubtedly give a neutral judgment for an 
aerial camera if it is being made by a neutral central organization. Therefore, 
I am in favour of it. 
I wish to thank Dr. Howlett in the name of the Swiss Society of Photo-