HIGH SPEED MOTION PICTURE PHOTOGRAPHY 399 



High speed motion picture photography is finding extensive apph'ca- 

 tion in industry where it is appHed to "motion analysis" of a variety 

 of manufacturing operations and to problems associated with the 

 design and performance of machinery. A particular value of this 

 method of motion analysis lies in the convenience and accuracy with 

 which space-time relationships of moving parts can be determined. 

 Individual frames can be enlarged as photographic paper prints or 

 projected onto a lined screen; in either case, the movement of parts 

 can be measured with a high degree of accuracy. Extensive applica- 

 tion is made in automotive and aeronautical engineering to the study 

 of problems associated with fuel combustion, vibration in motors, 

 airflow around structures and to propeller design and performance. 

 It is coming into use in the fields of biology and medicine, especially 

 in the study of muscular and nervous reactions. It has been applied 

 to microphotography in the photographing of biological specimens at 

 magnifications of 500 to 700 times at a taking rate of 1000 pictures 

 per second. 



In high speed photography one of the principal problems has been 

 the securing of adequate illumination of the subject. Exposure times 

 are of the order of one twenty-thousandth second or less for taking 

 speeds of 4000 frames per second. Artificial illumination must be 

 used and arc lamps and tungsten incandescent lamps are employed. 

 Special projection bulbs are secured which are greatly over-voltaged 

 during the few moments required in the taking of a picture. The 

 lamps are designed for short life and to operate as close to the melting 

 point of tungsten as is practicable. Two lamps are operated in series 

 during setting up and adjustment of the apparatus and full voltage 

 applied to both lamps at the moment of taking by the use of series- 

 parallel switching arrangements. The lamps are housed in specially 

 designed lighting units employing high aperture lenses or mirrors which 

 serve to image the source directly on the object at a desired magnifica- 

 tion. Provision is made for the reduction of heat by the use of water 

 cells of suitable thickness. Excessive heat in the image will frequently 

 cause distortion in delicate apparatus which must be avoided. One or 

 more lighting units may be employed depending upon the size of the 

 object being photographed, the taking speed, the lens aperture and the 

 film speed. Brightnesses of the order of 10,000 to several hundred 

 thousand foot candles are frequently employed. 



At Bell Telephone Laboratories, high speed photography has been 

 applied to a wide variety of problems associated with design and 

 performance of telephone apparatus. Pictures have been taken of 

 standard equipment and of experimental equipment in course of 



