Good Cheap Camera Filters
Early in the war, Edwin Land realized that color filters for aerial cameras could not be economically produced using conventional methods. The cameras required a Metrogon lens that covered a 93° field at f/6.3 and a yellow or red filter about six inches in diameter, having only a few wavelengths of error from flat. Such a filter often improves contrast by cutting out the light scattered by haze which is predominately blue.
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