Instruments Optical comparator with a scale graduated in increments of 0.1 mm or 0.005 inch.
Procedure Measure the length of the scale on the film image of the test target.
Divide this measurement into the confirmed length of the original scale. The value obtained is the actual reduction of the microimage. If there is no scale present, obtain the reduction by measuring the image of an object whose full size dimensions are known. Divide an equivalent full-size page dimension by its corresponding frame dimension to determine the effective reduction for computer output microfilm. Assess a defect in accordance with the Defect Classification Table.