E-11 

 advances approximately 8 meters over the seafloor between 

 consecutive frames. With the 250 watt/second strobe, the 

 camera's visible horizon is at a distance of approximately 

 5 meters. About 60% of track is photographed with about 

 40% of it being at light levels sufficient for scientific 

 analysis. 



The camera is mounted at an angle of 12 dowr from the 

 horizontal. Its lens has a focal length of 35mm, giving a 

 field of view of 54° x 33° at f 4.5. With ASA 200 Ektachrome 

 color transparency film, we used a shutter speed of 0.1 

 sec. and aperture settings between f 8 and f 11 to reduce 

 lens curvature distortions. The focus was optimized for 

 objects at a distance of 1.8 meters from the lens. The lens 

 is at a height of 0.7 meters above the seafloor when the sled 

 is in bottom contact. The strobe is at the same height 

 above the bottom as the camera, but is separated horizon- 

 tally from the camera by a distance of 0.6 meters, causing 

 some backscatter in turbid water while maximizing the even- 

 ness of the light field. 



The strobe is mounted to the right of the camera giving 

 the viewer of the film the impression of a low sun angle over 

 the right shoulder. Oblique angle pictures enhance the 

 ability to make biological identifications and to discri- 

 minate geological bedforms and bottom textures. The major 

 serious disadvantage of oblique photography is the inability 

 to accurately estimate the exact area of the region being 

 photographed (see discussion in Hecker, Blechschmidt and 



