OPERATIONAL INFORMATION 



Selection of Subject Material and Field Coverage 



Deep-sea photography with the NEL Type III Camera provides no pre-selection 

 of underwater subjects for study. Critical areas for study or investigation are selected 

 by latitude and longitude from existing bathymetry and navigational charts. Locations 

 for lowering the camera are determined by geographical position and by depth to 

 specified bottom features such as canyons, basins, escarpments, slopes, and ridges. 

 Figure 6 shows how the variable tripping wire and weight are adjusted to the fixed 

 tripping wire to give the desired subject distance, in water, of 6 feet, when the camera 

 is preset with an angular divergence of 30° from the vertical. Assuming use of 35-mm 

 film and a robot camera fitted with a lens of 30-mm focal length, the resulting field 

 coverage will be an elliptical area 5.7 feet long by 4.7 feet wide, or approximately 

 21 square feet. A special scale is used to make measurements of detailed features 

 within a 7y2-by-7'/2-inch photographic enlargement when the degree of magnification 

 and the camera-to-subject distance (after proper corrections for water refraction) are 

 known. 



Figure 6. Diagram of field of photographic coverage. 



