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ASNT Level III- Visual & Optical Testing

My Level III Self Study Notes

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1.5 Luminous Efficiency of Radiant Energy<br />

Many apparent differences in intensity between radiant energy of various<br />

wavelengths are in fact differences in the ability of various sensing devices to<br />

detect them. The reception characteristics of the human eye have been<br />

subject to extensive investigations and the results may be summarized as<br />

follows.<br />

1. The spectral response characteristic of the human eye varies between<br />

individuals, with time and with the age and health of an individual, to the<br />

extent that the selection of any individual to act as a standard observer is<br />

not scientifically feasible.<br />

2. However, from the available data, a luminous efficiency curve has been<br />

selected to represent a typical human observer. This curve may be applied<br />

mathematically to the solution of photometric problems.<br />

Charlie Chong/ Fion Zhang

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