... Focal length of the lensEffective aperture = (Set Aperture) x (1 + Magnification ratio) This ring set consists ... XG-a; X Series: X-700, X-600, X-570, X-500, X-370s, X-370n, X-370, X-300s, X-300, X-70, X-9, X-7a, X-7, X-1 ... , XM, XK, X ... Auto-Rokkor, MC Rokkor, MC Rokkor-X, MD Rokkor-X, MD Minolta, MC Celtic and MD ...