To convert one raster circle

Select Convert Circle.
Select the appropriate color mask.
Make sure the Round Off field is set to zero and the lock at the left of the Diameter/Radius option menu is off.
Identify the raster circle to be converted by entering a data point along its circumference.
The resulting vector circle follows the center of the raster circumference that is converted (or the circumference of the solid raster circle).
Note: Use the Round Off field to round off the resulting circle to specific increments. See Circle Recognition.