Anyway, the K-20 D's magnification factor is definitely 1.5X.
I think Canon has a 1.6x on some of their cheaper DSLR's, which have slightly smaller sensors.
Your questions about how to operate the camera with various lenses can best be answered by referring to the instruction book.
I have photographed the specific pages from the instruction book that deal with this.
Kindly refer to the attached photos for details.
Contact me if you have any other questions.