I recently purchased a Zone VI 5x7 Variable Contrast enlarger Type I on E-bay. Since I print on graded paper I never use the low and high contrast knobs on the VC control box. I am considering VC paper and I am confused on how to use the two knobs. The enlarger didn't come with an instruction book. For example: do I raise the low contrast knobs position to its maximum position and leave it there(or return it to its min. position)before I use the high contrast knob inorder to raise contrast? Or do you ever mix the two knobs together? Does anyone have a instruction book that could be copied or purchased? Thank you in advance for your help, Richard Sprengeler.