High-Speed Lens Motion-Picture Photography

a special type of motion-picture photography with a speed of more than 300 frames per second. Photography at speeds higher than standard (usually 16 frames per second) slows down the motion of objects on the screen. The factor of slowing is equal to the ratio of these two speeds. This phenomenon is used in scientific and technical research on fast movements and processes that occur rapidly.

As distinct from high-speed motion-picture filming, which is based on the intermittent movement of motion-picture film at a speed of up to 300 frames per second, high-speed lens photography is based on the continuous movement of the film or on the movement of the image itself with a fixed film (optical commutation). A sharp image is produced in shooting with moving film through use of an optical compensator, which rotates in the direction of motion of the film in such a way that a ray of light passing through the compensator always falls on the same spot in forming a frame. This technique makes possible production of up to 2 × 10⁴ standard frames per second on 8-mm film. Further increase in the speed of filming is made possible by decreasing the height and width of the frame (nonstandard frame) through an increase in the number of facets or lenses of the optical compensator or through optical commutation of the image. In the latter case, the image is formed in the frame by rays of light reflected from a rotating mirror onto a fixed film through lenses. Using this principle, it is possible to photograph on 8-mm film with a speed of up to 10⁵ frames per second. The transfer of the images from exposed nonstandard frames to frames with standard dimensions is done by optical printing or sequential rephotographing of the images of each frame on a duplicating machine.

The main difficulties in high-speed lens motion-picture photography are sufficient exposure on the light-sensitive material with very short exposure times (often millionths of a second) and synchronization of the camera start with the moment of the motion being photographed. A further increase in the speed of photography (up to 10⁷ frames per second) is being achieved by using grating methods.