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Aviation History
1942
1942 - 1802.PDF
232 FLIGHT AUGUST 27TH, 1942 AIR PHOTOCRAPHY IN WAR explosion with the actual bomb bursts during a night raid. Most people who have used a camera will know how important it is to esti mate the right exposure. This, again, is a job for the photographer, who must calculate and "set" the expo sure before the aircraft leaves the ground, for it is generally impossible to make alterations in flight. The problem of estimating exposures is much more difficult in aerial photo graphy than in ground work. The problems do not arise to any great extent from the type of subject or from the weather, for at high altitudes the weather is very much the same the world over and all subjects are alike. The chief pioblem lies in the fact that the exposures are usually made hun dreds of miles away from the base, and many hours after the cameras have been set. When it is remembered that light varies with time of day and period of the year, and also with lati tude and longitude, it will be seen that there are a good many factors to be thought of. Exposure tables of a sort were avail able at the outbreak of war, but, as the scope of operations widened, special tables were worked out based on service data which covered the whole globe. Copies of these tables are to be seen in every section, and are used in conjunction with the pilot's reconnaissance report, which contains the necessary meteorological information and the anticipated time and duration of the period over the target. With these data it is nearly always possible to make an accurate assessment of the exposure. Photo Map-making On his return from the sortie, the pilot records the actual conditions under which the exposures were made in the photographic reconnaissance report, so that on further reference to the exposure tables the photographer can check their accuracy from actual experience. Under adverse weather conditions, or when avoiding action has caused delay, the* resultant errors in exposure can still be partially corrected by giving the film special processing treatment for known under- or over-exposure. Processing in the R.A.F has been highly standardised, and is entirely carried out by the time-temperature method. By this means it is possible to produce uniformly high quality even in processing individual spools of film from day to day. On the small sections, which handle only short lengths of film, the spool developing unit is still employed, and fresh developer is used for each spool to ensure that no loss of quality results from stale or partially exhausted developer. A small army of photo finishers, airmen and W.A.A.F.s, are kept busy day and night turning out the prints for the various intelligence branches. Here, again, it is vital that quality shall be maintained. The intelligence officers are mainly concerned with microscopic detail in shadows and high lights and if photography is to play its part none of this must be lost. On small sections this work is done by expert photographers, but on larger sections machinery has again been brought into play, and automatic printing machines capable of handling up to 600 prints an hour keep pace with the ever-growing demand for more and more pictures. Although most of the requirements of the intelligence Interior of a photographic trailer with W.A.A.F. photographers at work in the printing room. The trailer is a completely self-contained developing and printing unit with its own hot and cold water system and air-conditioning plant. branches are fulfilled by contact prints from the negatives, map-making to scale requires accurately scaled enlarge ments of matched quality which can be mounted together to form a composite picture of a whole district. Even in peacetime and when flying conditions are ideal, the task is a tricky one, but in wartime, when the pictures may have been taken by different aircraft flying at different heights, the task imposes the most searching tests on the skill and patience of the photographer, and much depends on the personal care and attention which he bestows on his ground work. But since they know the great personal risks which the air crew have taken to bring back the photographs, some times with the grisly reminder of a camera full of bullet holes, the technical staff consider no pains too great to extract the last ounce of value from the negatives; and when they compare shots " before and after," and note the accurate destruction to which their work has contributes^' theirs, too, is the grim satisfaction that they are pulling their weight in the war. Non-photographic Heat-reflecting ^Mnt PAINT that reflects hpaf rays but not light applied to the rope of its new buses am •ay* is being ;oach%s by the alsoy buflage material. sported ^to have ams) abd buses tiieVcannot be n flight either White Motor Co. in trie United States as a The American Transit Association is recommended thawhe tops of all street^ c&t be painted with/inatvial of this readily seen or f£)otoj|raphed fro by day or at ni Paint of this Bnd/as 'JevWonfet^^ th* Arco Company, of Cleveland, Ohio, fkj6stre4ss| olwe-drlb in colour and reflects rays of wave-leng\nViJpnge\ than those of visible ,*ays, such as heat and infra-red\r»W \jk suitable not only for camou flaging army truckk ta*ks, ordnance and aircraft in wartime but also for insulatink motor coaches, buses; trams and railway cars against heat tran^ajssion injffae'ffime. The British GovernmenP'UliUOffbtedly is familiar with this type ol material, which is believed to be the kind used on aircraft ol (he air forces to make them nearly invisible in the beams of enemy searchlights.
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