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A photographic method for determining mineral reflectances in underground mines
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A photographic method for determining mineral reflectances in underground mines
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    "The Bureau of Mines conducted a study to (1) determine from laboratory tests the feasibility of a photographic method for determining reflectances that may be applied to measuring in-mine mineral reflectances and (2) formulate a procedure for collecting and analyzing the data. The method uses a 35-mm camera with automatic flash and a gray-scale reflectance standard to collect on film reflectivity data in underground mineral mines. After the film is processed, the data on the photographic prints are analyzed in the laboratory with a photometer. Test results show that the photographic method can provide values of reflectance within +/- 5 pct of full scale (full scale = 100 pct). The method's usefulness for determining reflectivity values within similar limits of absolute percent error at the lower end of the scale, however, has not been completely resolved by the study and consequently warrants further investigation. The method offers an acceptable means for collecting and analyzing reflectivity data for reflectivities at the higher end of the scale, i.e., 50 pct or above; it should be used with caution when reflectivity values are below 50 pct. Four films were evaluated; all gave relatively satisfactory results." - NIOSHTIC-2

    NIOSH no. 10005816

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