HIGH-SPEED KINEMA

Evening Star, Issue 18717, 20 August 1924, Page 11

HIGH-SPEED KINEMA

FILMING INSECTS DURING THEIR FLIGHT, M. Lucien Bull, sub-director of the Marey Institute in Paris, recently described at tho Royal Institution tho new apparatus by which kincraa pictures can by taken at tho rate of 25,000 per second. The highest speed for ordinary kinmna pictures was, ho pointed out, 300 per second, which was ample for everyday work, the method adopted being momentarily to stop the film as it was exposed. To obtain higher speeds various devices Imd been adopted, and the electric spark had two peculiar properties that gave it enormous value. In tho first place, it had a brilliance of from fifteen to twenty 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, tho duration of the spark was astonishingly small, and when pictures were taken at this rale it lasted only 1-200,000 of a second; it was, in fact, as if the sun shone on tho earth for a single day, and this day was followed by a night "of 250 years. Consequently sharp images could be obtained on the film'even though it was continually moving behind the lens at a very rapid rate. ,\I. Bull reviewed some of the early experiments at the Institute _ Marey with this method for photographing insects iu flight. The blue-bottle, ho said, behaved admirably. All that was necessary was to enclose it in a. glass tube fitted with a mica door, and to shine a bright light opposite the tube. The blue-bottle, walked down the tube, and flow straight to the light. By opening the mica door it exposted the film, and the exposure was stopped as the mica door fell back. _ Tho wasp was an exasperating insect ; it would go to the end of the tube, open the mica door, and then walk back again. The bee was equally exasperating; it would open the door, and then - eraa I about tho end of the tube. To secure « picture of a wasp in flight he had had recourse to tho drastic measure of shooting it out of a spring gun. Among many interesting pictures taken by this method, which M. Bull showed was tho bombardment of a soap bubhi with a paper pellet. The pellet could Iseen entering the bubble (which auto matically scaled up the hole made by i. entry), 'traversing tho centre of th bubble, and shattering the bubble as emerged. -■ The method had a great drawbackthat for mechanical reasons only \ci. narrow images could be obtained if i was desired to push the speed, soy, Dot; 10.000 to 25,000 exposures per second This difficulty had been overcome. In stead of moving the film, as was done i. all previous method?, the fmage was caon to a rapidly-moving mirror or other o : tical device, and reflected on to a si; Denary film placed around it. M. Bull demonstrated for the first tim«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 fcnmugh a glass bulb. As the bullet emerged it appeared to be larger than it was when entering, because of the pondered glass with which it was coated. Another remarkable, effect, of which no explanation could he given either tno Institute Maroy or by tlie artillery officers for whom tho experiments were condne, ted, was that whom a bullet shattered a piece of wood tho wood fragment achieved a velocity greater than that of the bullet.