Friday July 28 1972, 15:45 
The Commission President remarked that the increasing use of colour justified this special session. He 
introduced S.W. Dossi to present his Invited Paper “Colour” (A Report), and moderate a panel on the 
subject. 
S. Dossi referred the audience to his published Paper, and went on to mention some recent developments. Two 
new films, one black and white, and one colour, will be released shortly for shoreline photography in 
hydrographic work. W. Tayman has written a draft report on calibration of cameras for colour photography. 
H. Yzerman had told him that filters were available in Europe to isolate any part of the spectrum with uniform 
illumination. S. Dossi showed examples of the Engineer Topographic Laboratories (USA) experimental colour 
orthophotomaps of Fort Sill, Oklahoma. Batelle Memorial Institute have recently published a colour 
photography bibliography. 
R.K. Roedel, in summarizing his presented paper, described modification which had been added to a 12" K17 
camera to provide sensitometric control. On every camera frame were printed 3 control exposures: (1) a 10 
step sensitometric wedge exposed by a Xenon flash lamp; (2) a 10 step sensitometric wedge exposed by 
integrated incident daylight; (3) a single spot exposure representing light reflected from the ground, averaged 
over the field of view of the camera. The camera exposure was automatically controlled by means of a cadmium 
sulfide cell. He showed a number of examples of the effects obtained by balancing colour transparencies in 
various ways based on the 3 control exposures. 
W.V. Trollinger summarized his presented paper, “The Role of Colour Photogranhy in Natural Resources 
Exploration". He showed panachromatic and colour photographs, pointing out examples of how the colour 
information made the interpretation of rock types and structures more reliable, easy and rapid. He then showed 
colour space photographs which illustrated the advantage of an enlarged perspective to locate geotectonic and 
structural features. He suggested that there was great potential for high quality space colour photographs. 
C. Kraft summarized his presented paper on *Achromatic and Chromatic Stereoscopic Performance’ of the 
human eye. He briefly discussed the discovery and history of ‘““Chromostereopsis’’, an effect which results in 
co-planar objects of different colours appearing to be at different distances. He described a sophisticated test 
procedure which he had used for evaluating stereoscopic accuracy. It was found that about half of the observers 
saw red as nearer, and half saw blue as nearer. There was only slight correlation between chromatic and 
achromatic performance. He explained the chromostereopsis effect by the chromatic aberration of the eye, and 
the facts that the fovea is not on the optic axis, and the iris may be somewhat decentered. He concluded that 
to use operators most effectively on colour stereoscopy, it would be necessary to measure the individual 
characteristics of the operators, and perhaps modify the equipment to their individual needs. 
M. Scher confirmed that when the U.S. Geological Survey experimented with colour, some operators 
experienced fatigue and even sickness. 
S.H. Collins warned that people looking for the colour effects described with simple magnifiers and 
stereoscopes would be likely to find the visual effect confused by the chromatic aberration in simple lenses. 
C. Kraft agreed that such effects would arise in simple instruments, and even in some more complex ones. 
The meeting adjourned. 
Saturday July 29 1972, 10:45 
The Commission President said that each of the two subjects to be covered this morning, Photogrammetric 
Material” and ‘Geometry of Images’ would have been worthy of a session by itself, but that sufficient time 
for this had not been available. Since J. Cruset had been unable to attend, he asked J. Ducloux to present Mr. 
Cruset’s Invited Paper, “The Photographic Materials, their Characteristics and Processing from 1968 to 
1972”. 
The Commission President recalled the Resolution at the XI Congress asking for a study of image deformation 
problems. This had led to a Conference on Image Deformation in Ottawa about one year ago, at which H. 
Ziemann was the Commission I representative on the Programme Planning Committee. The Commission 
President then called on H. Ziemann, who discussed and summarized his Invited Paper, “Image Geometry - 
Factors Contributing to its Change”.