The answer
In Front surface tracking, the bevel crest or groove centre is held at a constant distance from the lens front surface. This differs from Distributed bevel or Distributed groove, which positions the finish in proportion to lens thickness.
Filed under Settings & modes
The tracking modes sound similar because they all control the position of a bevel or groove, but they use different references.
- Front surface tracking: keeps the bevel crest or groove centre at a constant distance from the front surface.
- Rear surface tracking: uses the rear surface as the constant-distance reference.
- Distributed bevel or Distributed groove: positions the finish in proportion to lens thickness, measured with respect to the front surface.
- Lens curve tracking: adjusts the camber of the bevel or groove.
For High-base bevel and Step bevel, the front surface tracking value must be between 0 and 1.3 mm. Selecting this mode therefore changes the geometric reference used by the machine; it is not merely a visual display option.
