TVDC-500 TAPPI Visible Dirt Count Tester is a computer-scanner based image analysis system designed to measure visible dirt present in pulp, paper, tissue paper and paperboard conforming to standard methods including TAPPI T563 and ISO 5350-4. The tester determines the level of dirt in samples in terms of Equivalent Black Area (EBA) of dirt specks within the physical area range of 0.02 to 3.0 mm² reported in parts per million as well as the number of dirt specks per square meter of sample.