Night Vision Current Research and Future Directions, Symposium Proceedings (1987) / Chapter Skim
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Appendix A: Testing Night Vision: The Military Experience During and Following World War II
Appendix A: Testing Night Vision: The Military Experience During and Following World War II
Pages 319-332
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From page 321... ...
highs blindness was of course a wellknown clinical syndrome, but there were no recognized standards that could be applied to detect mild cases or to compare normal individuals. The safety of a naval vessel could not be left in the trust of a lookout whose night vision was even moderately impaired, and men selected for night reconnaissance flights should certainly be ~r.en whose visual senses were as keen as could be found.
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From page 322... ...
As research continued, showing the two segments, rod and cone, of the dark adaptation curve, the word "adaptometer" came to be assoc iatea with the measurement of dark-adapted thresholds for light. Because adaptation slows and ceases after about 30 minutes in the dark, it seemed that the f inal, steady level might be taken as representative of the indi~ridual's night vision capability.
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From page 323... ...
Whenever c ircumstances smi led on an outdoor range and a number of men were run through the course under what seemed to be reasonably constant cond itions of lighting, motivation, and experience, their scores were eagerly tabulated and compared with scores by the same men on the more precisely controlled indoor tests, tests that had them doing more artif icial things like detecting dim lights, determining the orientation of standard f arms, or reading letters.
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From page 324... ...
Changes in the voltage, for example, change the color temperature of the light which in turn can produce marked deviations in the scotopic luminance. The wide range of nighttime luminances requires adjustment over many log units of intensity, again requiring considerable skill in the means of adjusting ano maintaining such a range.
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From page 325... ...
The Hexagon, operating over a range of luminances and employing a variety of targets, appeared to be based upon the second assumption. However, it spread people on a scale whose units were obscure; they indicated neither the variation in form perception or acuity among observers at one, standard light level nor the amount of light required to perform a standard task.
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From page 326... ...
The target ship would then retreat beyond view and come in again. It was hoped that several such runs would provide performance measures for comparison with scores generated from the same men on a dozen or so night vision tests that had been administered back at the base.
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From page 327... ...
, a device developed within the Personnel Research Branch of the Adjutant General's Office (Uhlaner and Zeidner, 19611, was that testing carried out at higher mesopic levels, at which rod and cone vision were both involved, would be as useful as purely scotopic for the purpose of predicting performance at ~ low light levels.. It thus circumvented the need for time-consuming dark adaptation and did not require specialized dark rooms for testing.
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From page 328... ...
the remarkable high agreement between sensitivity and acuity measures at the lowest light level ; (2) the fact that the correlation was best at this light level, which argues age inst any incompatibility of the functions being measured at low scotopic levels; and (3 ~ the slow but ultimately precipitous decline in cor relation with absolute threshold as the photopic level is approached .
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From page 329... ...
Nor can a naive sub ject be trusted to select the optimum peripheral angle for each condition. Thus in choosing a procedure, the tester must look ahead to consider the use to be made of the obtained information.
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From page 330... ...
REFERENCES Berry, W 1949 Review of Wartime Studies of Dark Adaptation, Night Vision Tests, and Related Topics.
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From page 331... ...
L 1954 Effect of different preadapting luminances on the resolution of visual detail dur ing dark adaptation.
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