TAPPI Dirt Count as an Index of Cleanliness, 1993 Process & Product Quality Conference Proceedings
B. D. Jordan
Since the TAPPI dirt count is measuring an appearance attribute called “cleanliness” it should either be measured visually or the visual task should be emulated closely with image analysis. Black equivalent area depends upon both the physical area of a speck and its local contrast, so measurements with a transparent dirt scale will differ from measurements made with the white TAPPI card. This function of contrast and area can be programmed easily into an image analyzer. A particular kind of local shading correction emulates the way the eye adjusts to reflectance variations in the sheet.
TAPPI Dirt Count as an Index of Cleanliness, 1993 Process & Product Quality Conference Proceedings
