Chromatic errors in photographic material are 10 times the chromatic aberrations of the optics. Even 
contact copying of colour can cause colour fringes. Colour film has three emulsion layers, and their 
performance requires study. 
Mrs. Norton said that a double image was unusual in a good quality camera. She suggested that a poor filter 
or a strain in a lens might cause trouble. 
The meeting adjourned. 
Monday July 31 1972, 10:45 
The Commission President said that photogrammetry will become an important tool in underwater 
exploration in the search for food and underwater resources. He introduced G.T. McNeil, Chairman of the 
Underwater Photography Committee of the American Society of Photogrammetry, who presented his portion 
of the Invited Paper * Underwater Photography", and called on his co-authors, or their substitutes, to present 
tneir portions as follows: H. Seifert, * Underwater Cameras, Lenses and Housing"; L.H. Bassage, ‘“ Films for 
Underwater Photography" C.J. Buchanan presented **Underwater Lighting Advancements’’ by J.W. Harford: 
J.J. Welsh, “Underwater Photography and Photogrammetry Bibliography’; J. Pollio, “Systems on Underwa- 
ter Vehicles’. 
Many of the presentations were copiously illustrated with interesting photographs. 
G. McNeil asked for open discussion from the panel. 
C. Buchanan pointed out three problems in underwater photography: 
(1) a more efficient means is needed for controlling light distribution over large areas; 
the desirable film spectral response depends on the distances involved; more sensitivity is needed in the 
blue - red light should be eliminated, since it contributes largely to back-scatter; 
no plastics can withstand long the high intensity light from Xenon flashlamp, and this results in various 
engineering problems, for example, a durable gasket material is needed. 
He also suggested that other people consider, as an alternative to stronger lights, the possibilities of 
higher sensitivity, for example, by image intensifiers. 
J. Pollio said that much of the resolution loss in imagery is due to scattered light reducing contrast. This created 
a problem in selecting points on a sea bottom lacking in prominent features. 
He mentioned needs for faster diving vehicles, better illumination, more precise cameras, faster cycling 
of cameras and strobe lights, film flattening, and automatic data processing. 
The Commission President thanked the panel for their illuminating and fluid presentation. He mentioned a 
paper, “Optics for Photogrammetrists"", dealing with projective geometry as related to underwater optics, by 
Professor Zakaznov, who offered to send copies if requests were directed to Mrs. Norton. 
J. Hóhle referred to his presented paper, “Methods and Instruments of Multi-media Photogrammetry’, and 
mentioned that analytical methods must be used for underwater triangulation as is done in Germany, Sweden 
and Denmark, with an accuracy of 5 jum at the negative. Calibration is done under operational conditions, 
using either a test field, or without a test field, by 3 convergent photographs of the same area. 
H. Seifert described the U.S. Navy development work on an underwater camera calibrator. 
Mrs. Norton asked J. Pollio if film flattening was a major problem. 
J. Pollio said that it was. Good flattening devices were not used, and should be used to improve accuracy. 
Another requirement was keying of the camera to its case for consistent positioning. 
C. Buchanan pointed out that all camera materials change dimensions under pressure at operating depths. At 
present they have no way of calibrating under high pressure. He also mentioned that the camera must be taken 
apart for cleaning after each mission, which creates problems due to changes, such as decentering. He suggested 
that the pressure window have water on both sides so that its bending and displacement would not affect 
distortion, and its repositioning would not be critical.