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View-box is the last and important but often neglected link in the imaging Process. The quality assurance programme for view-boxes includes the measurement of the intensity of light-output (luminance) in Candella/m2 and the extent of variation in luminance (inhomogeneity) over the front surface of the view-box. An expensive instrument, photometer, is required to conduct both of these tests. Instead, an inexpensive Light Dependent Resistor (LDR) in combination with Ohm-meter may be used. The importance of quality assurance checks is indicated by the fact that majority of view-boxes (37.5%, 36 out of 49) had luminance less than 800 cd/m2, while the recommended level is about 1000 cd/m2 or more. Again, 55% view-boxes (27 out of 49) were found with inhomogeneity in luminance more than 10% while the permissible limit is up to 10%.
