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Aviation History
1941
1941 - 1774.PDF
A MIXED BAG : Illuminated views from above and below of two enemy fighters, a German troop transport and our most frequently used Coastal Command type. (x) Glare. Introduction of light between the eye and the object. These five stages affect the presentation of the object viewed. (xi) Movement. : •' (xii) Reduction of time of exposure. These last two stages affect the exposure of the object. (The above twelve stages in the use of letterpress may be combined to produce not less than 500,000,000 separate exercises.) It is now important to get the student away from the idea that the object of visual training is reading under difficult conditions The brain is now accustomed to expect print, and appreciation suffers accordingly. Hence the next step in visual training is the introduction into the exercises of objects which are not what they at first sight b FLIGHT August 7th, SPOTTIh appear to be. Concealed letters and other matter designed to invite the question, '' What is there that I do not at first see? " Success in this stage depends largely upon the extent to which the instructor can stimulate the man's brain in contest with him. If correctly done, we in this way combat careless vision. The man begins never to accept what he sees with- out close study for hidden detail. Design of this type of sight card is limitless, and all the stages of con- fusion can be introduced singly or in combination so that variety is endless. We must now get the man away altogether from letterpress, which has hitherto been our sole means of checking results. The next step in visual training, therefore, con- sists in presenting to the man, either on cards or out of doors, objects or views inviting the ques- tions: (i) What is it? (ii) How many are there? (iii) What are they? Binoculars An expert has stated that it would require two years to make a man really proficient with binoculars, and that he could not guarantee to raise a pupil to the pro- hciency 01 a Highland ghillie with a telescope in a lifetime. Binoculars are classified by field and magnification. The latter affects the standards to be expected. The field of view may vary in different glasses from 7 deg to 12 deg. The mag- nification of binoculars is marked (for example) '' MAG 7 " or simply "X7," implying " Mul- .tiply by 7." With bin- oculars X7 the standard eye should easily read r6in. letter press at 70 yards. There are, however, certain points about the use of binoculars a spotter must know in order to achieve these results and exercise himself in telescopic vision. First, never focus binoculars on an object less than 70 yards distant when about to use them for long-distance work. For effective work the binoculars must be perfectly clean inside and out. Focusing should be done one eye at a time, not by closing one eye, but by covering the end of one telescope and focusing the other. The final adjustment is made with both eyes. Never strain the eyes; look naturally at the object through the binoculars with the muscles of the eye in the condition for unaided long-range vision. By visual exercises with and without binoculars, carried out little and often, it is possible considerably to improve the otherwise intangible link between eye and
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