Specify the threshold for how much contrast (difference between light and dark) is required in the image to identify something as an edge. Input the value or change the value using buttons.
The default value is 10, and the specifiable range is from 1 to 200.
If the average contrast of the contour of the found region is below this threshold, then the region will not be considered as a flaw. Faint flaws can be detected when a lower threshold value is specified, but some flaws may be recognized larger and the contour fuzzier. On the other hand, faint 'flaws' are not found when a higher threshold value is specified, and only apparent flaws are found. If the contour of a flaw is fuzzier than you expected it would be, increase this value.