A BACKGROUND OF THE WAR

Dominion, Volume 34, Issue 137, 6 March 1941, Page 6

A BACKGROUND OF THE WAR

Weapon Of Revelation THE AERIAL CAMERA

Au important weapon in warfare is the aerial camera. Many thousands of accurate shots are “taken” by the photographic guns of reconnaissance planes that are of immense importance in the operations of the Air Force, the Navy, and the Army. .To the uninitiated aerial photographs frequently convey very little, but to the trained “reader” they tell a vast deal. From time to time, the British authorities release for publication some remarkable aerial photographs which impress the most casual observer. There were, for example, the splendid pictures showing the tremendous damage wrought to Italy’s battle fleet at Taranto by the torpedoes of the Fleet Air Arm. These were a complete answer to the Italian claims that little damage was done on that occasion. From Great Heights

Because of the longer range and greater accuracy of ground guns aerial photography in this war has been more difficult than in the last, despite the progress made in equipment and methods, says the aeronautical correspondent of “The Times.” In the last war a reconnaissance machine was reasonably safe at 8000 ft. to 10,000 ft., and from that altltpde good photographs could be obtained. Now, unless it is to risk being shot down, an aircraft engaged on this work over stronglydefended areas must operate at 20,000 ft. or more. z Such an altitude brought obvious handicaps. Pictures taken from a great height naturally decrease the scale and the detail of the objects on the ground. To “bring up” those details long-lens cameras were employed, but these in turn had their drawback, for they called for more accuracy of aim and Increased the risk'of missing the mark. Bigger cameras were necessary, more than one in an aircraft, and they were not easy to install. Photographs are not only used to show the consequences of bombing raids; frequently they lead up to them. Much of the information about enemy activities, such as ship and troop movements, is gained from photographic reconnaissance flights. As soon as pictures indicate the existence of an important target the R.A.F. Bomber Command get busy, and afterward the scene of the operations is often photographed again to make sure that the raid was successful. The Night Lens

Air photographs can be taken at night, though searchlights, bursting shells, and incendiary bullets can and do sometimes defeat the camera. If the weather is good and the ground defences not too active the’ R.A.F. can guarantee a “readable” night photograph taken from as high as 4000 ft. Flash bombs are employed to illuminate the objects on the ground, and the flash automatically closes the camera shutter by means of a photo-electric cell.

After careful examination of enemy cameras and the pictures taken by them our experts are convinced that, generally speaking, we are ahead of Germany and our lenses superior. The laboratories, the advice, and the experiments of the two largest photographic firms in the country are constantly at the disposal of the R.A.F., so that not only in cameras and films . but in processing methods improvements are always being made. Faster and better films permit of wide margins of error in exposure, either “over” or “under,” and yet give “readable” photographs. The laboratories have contributed emulsions for films of increasing speed and finer grain, panchromatic coatings that make for greater sensitiveness to the red end of the spectrum, infra-red films, and a bromide emulsion w’hich provides for either contrasting or soft effects in printing. Precision Cameras

The aerial camera is now a ’’precision instrument,” simple to handle, and standing up to hard wear and tear. When employed in taking vertical photographs it is electrically operated and starts at the turn of a timing switch. The control unit continues to make exposures at get intervals, either until it is switched off or the film runs out. If a few exposures are enough, only' a control button need pressed at the time intervals required. After the release of the shutter the mechanism automatically drops into mesh, rewinds the shutter, winds over the exposed portion of the film, and changes the number on a veeder counter.

The effect of extreme changes in temperature is overcome by a heating arrangement which prevents excessive contraction in the shutters. In the past this was the principal cause of jamming at high altitudes. New mountings, and increases in the speed of the shutters and of the panchromatic emulsions, have overcome vibration and the forward movement of the aircraft. In machines travelling at 250 miles an hour successful vertical photographs have been taken from as low as 200 feet.

Processing of air films has been quickened by means of a series of tanks into which the exposed film is put at one cud and comes out at the other developed, fixed, washed and dried ready for printing. Printing is done from rolls of bromide paper, sometimes as much as 1000 feet long, and the R.A.F. has plant capable of turning out 500 prints an hour from any negative. Firing By Camera

The camera does other work besides intelligence. Prospective fighter pilots and air gunners are taught to fire by camera, and the cine-camera guns now used are a great advance on the singleshot camera gun. Bomb-aimers also get practice in sighting and aiming at actual objectives by the “stimulation of bombing photography." Bombing practice at night is made possible by the infra-red sensitive film.

The men who collect the photographic evidence for the R.A.F. receive a special training. Although the actual exposure of a plate or film is the first step in the production of an air photograph it is by no means the only essential one. The various operations which follow it call for much technical knowledge and skill; tackled wrongly, they would present many different possibilities of failure. Initial training is given at the R.A.F. School of Photography and in order to complete the course successfully men must attain a high standard of knowledge and proficiency. The value of an air photograph depends, first, on the amount of information to be obtained from it; and, secondly, on the speed with which the finished print can be produced. The better the quality of the picture the easier, the more rapid, and more accurate the work of the “reader” who extracts military information from it; Often the quickness at which photographs are in the hands of the “readers” determines their value to the bombers.