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124 DISCUSSION ON PRESENTED PAPERS 
of objects can be accomplished very easily and 
higher graded aspects at which you are getting 
is an inexplicable intermixture of the capabili- 
ties individual, and photo quality. 
Other COMMENT: It seems to me there are 
two things linked up here. One is talking about 
the quality of the photograph and one is talking 
about measuring the photo quality in terms of 
interpreter judgment. 
CHAIRMAN: Yes, but not necessarily for a 
common purpose. This is, I think, a point of 
view that needs to be clarified. The point is this. 
Mr Olson has a photograph here which he uses 
in his forestry. Mr Jones wants to borrow this 
photograph for use in his particular purpose in 
the Army, and Mr Olson wants to tell Mr Jones 
how good a photograph it is. But he does not 
want to tell him that he can identify a tree on 
it because this does not mean anything to Mr 
Jones, or it does not mean as much to Mr Jones 
as it might to some one else so he gives him a 
number. Now, to get this number — he does not 
get it in the course of his interpretation — he 
gets it by an entirely separate operation. He puts 
it under a variable magnifier, one of those new 
zoom types — and he slowly increases the mag- 
nification, picking the finest detail that he can 
see on there until the detail starts to disappear, 
then he reduces the magnification and he sees 
^ Tinaudible]... 
Well, this photograph is a No 25 photograph 
and he tells Mr Jones that this is a basic scale 
of 1/10,000 and it is a 25 character photograph 
—, that this may convey to him an idea of what 
size of groups he may be able to identify. 
COMMENT: Yes, but I honestly think that the 
same thing pertains if you start from a very 
gross magnification where you see nothing and 
this is the procedure you would use because as 
it decreases one knows the detail he is looking 
at. One can actually experiment and distinguish 
in his mind the fact that he has seen it. 
So let us assume we start from the very gross 
magnification where the blur is too great and 
one brings it down and is looking for this com- 
ponent of identification. This is bound up with 
the photograph, the particular component of the 
photograph the man is looking at and with the 
man himself, I don't see how you can separate 
them out. 
COMMENT: I would suggest to you that 
...[inaudible]... Development Centre spent a 
number of years trying to put a quality label on 
a photograph and they are trying to identify by 
psycho-psychical means. As yet I don't know of 
any convenient measure.