DOI - aspect of gloss characterized by the sharpness of images of objects produced by reflection at a surface. (ASTM E 284)
In general, as DOI decreases, reflections at the sample surface appear to spread or fuss. This can readily be seen along the reflection's perimeter. The Surface Analysis System's DOI algorithm measures this spreading phenomena.
An area is determined from each of the image reflections. A circle is created that has the same area for each of the two images and is drawn above/right. The difference between the Reference radius and the Sample radius represents the DOI loss.