HIGH-SPEED CINEMA.

Otago Daily Times, Issue 19261, 27 August 1924, Page 5

HIGH-SPEED CINEMA.

FILMING INSECTS DURING THEIR FLIGHT. M Luoien Ball, sub-director of the Marey Institute in Paris, recently described at the Royal Institution the now apparatus by which kinema pictures can be taken at the rate of 25,000 per second. Tho highest speed for ordinary kinema pictures was, ho pointed out, 500 per second, which was ample for every-day work, the method adopted being momentarily to stop the film as it was exposed. To obtain higher speeds various devices had been adopted, and the electric spark had two peculiar properties that gave it enormous value. In the first place, it had a brilliance of from 15 to 20 times that of the sun. so that it would affect a photographic film much more rapidly than the sun could do. In the second place, the duration of the spark was astonishingly small, and when pictures were taken at this rate it lasted only 1-205,COOths of a second; it was, in fact, as if the sun shone on the earth for a single day, and this day was followed by a night of 250 years. Consequently, sharp images coula be obtained on the film oven though it wa-s continually moving behind the lens at a. very rapid rate.

M. Bull reviewed some of the early experiments at the Institut Marey with this method for photographing insects in flight. Tho blue-bottle, lie said, behaved admirably. All that was necessary was to enclose it in a glass tube titled with a mica door, and jo shine a bright light opposite the tube. The blue-bottle walked down the tube and flew straight to the light. By opening the mica door it exposed the film, and the exposure was stopped as tho mica door fell hack.

Tile wasp was an exasperating insect; it would go to the end of the tube, open the mica door, and then walk hack again. The bee was equally exasperating; it would open the door and then crawl about the end of the tube. To secure a picture of a wgsp in flight he had had recourse to the drastic measure of shooting it, out of a spring gum Among many interesting pictures taken by this method, which M. Bull showed, was the bombardment of a soap bubble with a paper' pellet. The pellet could bo seen entering the bubble (which automatically sealed up the hole made by its entry), traversing the centre of the bubble, and shattering the bubble as it emerged. The method had a great drawback—that for mechanical reasons only very narrow images could be obtained if it was desired to push the speed, say, from 10,000 to 25,000 exposures per second. This difficulty had been overcome. Instead of moving tho film —as was done in all previous methods — tho imago was cast on to a rapidly-moving mirror or other optical device, and reflected on to a stationary film placed around it.

M. Bull demonstrated for the first time in public photographs taken at the very high velocity of 18,000 to 20,000 exposures per second. One of the most curious was the picture of a bullet passing through a glass bulb. As the bullet emerged it appeared to be larger than it was when entering, because of the powdered glass with which it was coated. Another remarkable effect, of which no explanation could bo given either by the Institut Marey or by the artillery officers for whom the experiments were conducted, was that when a bullet shattered a piece of wood the wood fragments achieved a velocity greater than that of the bullet.