OCR Text |
Show Aerial Pltterajpli r 1111111 r 51 " - v- ' ' ' r s 3 F ' ? " " x - ' ' -" " ' d 4 By ELMO SCOTT WATSON 1 iJ L a N MAY of last year the announce- jl' T V a J 1 ssjn" 17" T" ment was made that the United Sd i " v'S. liij, XL States army had added another bril- s" 4 '''O'S. 1-, liant achievement to the record Sj'A i ' 4 ' "SV WS which makes valid the boast that 0? 5 I ? , g - , XX P Ji "the army does other things besides '4 - M J I ' f-n 4 " -' -i-Xg.J fight." A new record in long dis- J - K r -wr , L , v f X tance aerial photography had been f xws T'ftA ",' -"s'-&'.-1l eet by the air corps of the army when Capt. A. U 4 Af - !f t ' " "IT la TP. Stevens, photographic expert, succeeded in "IL S f v l f j taking a picture covering a distance of 270 V .T ,"V f" V- " ' 1 miles in a single exposure. In 1929 Captain - 4 1 ?'4 -r-;s- j Stevens had set a long distance photographic U L,' - , " CT.11--- " "ll 1 3-ecord when his camera registered objects 227 4 ',,:av " j? 1 miles away from the camera eye but his 1930 ; X v4w w" - " .. flight in a plane piloted by Lieut. John D. L, Z,JJ l" " ll;r t Corkille over Crater lake in Oregon added more f( " - ui1-5ci than 50 nrles to that record. WHrt, Wr Unon his return from this flirt. Captain S, 4 By ELMO SCOTT WATSON Cp N MAY of last year the announce-fTT announce-fTT T- ment was made that the United y States army had added another bril-liant bril-liant achievement to the record EyJ which makes valid the boast that & j; "the army does other things besides g5-i-;.J fight." A new record in long distance dis-tance aerial photography had been set by the air corps of the army when Capt. A. "W. Stevens, photographic expert, succeeded in taking a picture covering a distance of 270 miles in a single exposure. In 1929 Captain Stevens had set a long distance photographic Tecord when his camera registered objects 227 miles away from the camera eye but his 1930 flight in a plane piloted by Lieut. John D. Corkille over Crater lake in Oregon added more than 50 m'les to that record. Upon his return from this flight, Captain Stevens declared "While I am very well satis-lied satis-lied with the results obtained on this particular mission, I am inclined to believe that it will only be a matter of time before we will develop de-velop s camera that will record even greater distances. Before we can use it, however, we must have a photographic plane that will take tis considerably higher than '20,000 feet because from that altitude even an object as tall as Jlount Rainier will sink below the horizon at 300 miles. "Shooting at Mount Rainier from a distance greater than that between New York city and Washington Is much like shooting at the moon, 'With the difference that you can see the moon. The principal task is to aim the camera in the general direction you believe your objective to be, snap the trigger and hope for luck." What f" ""luck" the army captain had on this expedition was revealed by the remarkable photograph which Is shown above. Another achievement in this new scientific marvel of aerial photography, which was not so much a matter of luck, was demonstrated during the army air maneuvers over New York city during May of this year, the results of -which are shown in the photographs numbered num-bered three and four above. As explained in the captions, these pictures were taken by exploding ex-ploding a bomb containing enough magnesium powder to make a 3,000,000.000 candlepower Hash and snapping the shutter at the height of illumination. It would seem to be an easy matter to drop a flashlight bomb and at the moment of the explosion ex-plosion to take the photograph. Since, however, there is a definite relationship between the altitude alti-tude of the airplane and the height at which the bomb explodes, it is not so simple. Night photographs can be taken only at comparatively Jow altitudes. Measurements of the photographs taken over New York showed the airplane to have been flying at only 1,500 feet, although night photographs could be taken effectively up to around 3,000 feet. The lens cannot be left open until the bomb explodes because lights from the ground would blur the plates or film. The only thing the air camera man has to do at night is to release the bomb ; the rest of the details are taken care of automatically. The bomb, containing twenty-five pounds of magnesium magne-sium powder, is checked in its fall by a small parachute and a time fuse sots the Interval from the release to the explosion. As the bomb bursts the camera's shutter Is automatically tripped by an ingenious mechanical device. Before the World war the science of aerial photography, except for a few cases, most of which were unsuccessful, was virtually unknown. un-known. It took on added importance early in the war and developed rapidly as the airplane became such an important factor in waging successful battles. But it has been since the war that its most rapid development has taken place and that development in this country has 1. Two hundred and seventy miles of wide open spaces! A photograph of Mount Rainier taken from over Crater lake, a distance of 270 miles, by Capt. Albert VV. Stevens from an army air corps plane piloted by Lieut. John D. Corkille. To get the "shot," the two army airmen air-men flew at 20,000 feet for nearly five hours in a temperature of 20 degrees below zero and came down only when their supply of liquid oxygen was exhausted. Some of the mountains shown in the picture are: 1. Mount Rainier, 270 miles; 2. Mount Hood, 200 miles; 3. Mount Jefferson, 175 miles; 4. Three Sisters, 125 miles; 5. Diamond Peak, 50 miles; Crescent Lake, 45 miles. 2. Captain Stevens and Lieutenant Corkille of the United States army air corps with the large aerial camera used in taking high altitude photographs. This camera uses a 30-inch focal length lens of special construction. 3. This night photograph of lower Manhattan, Manhat-tan, New York city, was taken by Captain Stevens from an airplane piloted by Lieutenant Corkille at an altitude of about 1,500 feet.. A bomb containing sufficient flashlight powder for a three billion candlepower flash was dropped from the plane and the picture taken with a specially constructed camera equipped with an automatic device for exposing the film at the height of illumination. 4. A night photograph of the Statue of Liberty Lib-erty and Fort Wood on Bedloe's island in New York harbor taken in the same manner as described de-scribed in No. 4. All photographs, courtesy United States Army Air corps. 3 been carried forward mainly by the United States army. Although the army is chiefly interested In map-making and intelligence photography, each of which requires a different technique, it has many times sent Its camera men and planes to co-operate with other government agencies. The army has Indirectly aided commercial aerial photography by developing the best in technique and in precision of the instruments. In addition to military work, aerial surveys are used for a large variety of operations. Few public utility companies "would consider putting down a new power line without first having an aerial survey made. Aerial photography Is also in demand for forestry services, geological surveys, harbor developments, highway and "traffic surveys, and all manner of city uses, from planning and zoning to tax equalization. The cameras and equipment used for civil aerial surveying and for the production of aerial photographs as illustrations have been Improved but little during the last ten years, because the ordinary air camera, operated at relatively low altitudes, meets all usual requirements require-ments at a small cost This is not the case with military photography, and so it is in this branch that the latest developments are found. Perhaps the most interesting development lieb in the use of long-range or high-altitude cameras, cam-eras, the same technique being used also for lower altitude work through fog. In high altitude alti-tude work the camera must have a long focal length (the distance from the nodal point where the light rays cross, between the two lenses to the surface of the plate or film). With a short focal length it would be possible for the camera to "take the whole world," but the detail would be too small. A camera with a long focal length, on the other hand, while it will not take more than about thirty-three square miles from an altitude of approximately 33,000 feet, gives such clearness of detail that the negatives may be readily enlarged to ten diameters." If the camera is tilted an oblique photograph is taken that Is, a photograph which is progressively distorted as the objects taken are distant from the lens. Tremendous distances have been covered in this way and objects have been taken which were not visible to the naked eye, because aloft there is almost always, even on a clear day, a certain amount of ground haze. Several refinements are necessary, however, before these photographs may be taken. The camera must be fitted with a special film sensitive sensi-tive only to infra-red rays below the visible spectrum that is, the long wave lengths which go through fog easily. This condition is met by taking ordinary gelatine film and Immersing it in a solution of kryptocyanine. The next requisite Is a special type of filter, so dense as to have the opaqueness of rubber. All lenses have to a greater or less extent the property of a prism ; that is, they break up the white light into spectra. It is necessary under given conditions to use a filter to eliminate the active colors( such as violets, blues and greens) and restore the light to white. By Increasing the opaqueness of the filter more of the visible spectrum is eliminated, and it is possible to eliminate It altogether. This Is what has been done in the cast of the long-range camera. Through its filter only the infra-red rays are admitted, and as ground haze or smoke Is no obstacle to them, objects are recorded on the film which are invisible to the naked eye. In this way Captain Stevens was able to photograph photo-graph Mount Rainier from the record distance of 270 miles, the peak jutting up above the horizon, though It was miles beyond it. In the taking of photographs for map-making a special technique has had to be developed, equally applicable to military and commercial purposes. It is not enough to sight the camera and trip it; all sorts of tilings have to be determined de-termined before the photograph can be taken. Because only the center of each photograph can be considered anything like optically perfect, a large number of overlapping exposures have to be made. by Western Newspaper Union.) |