This is a "back-hack" lens, left over from converting a Sonnar to Leica mount. So the J-3 optics gets made into Contax mount. Then into an Amedeo Adapter, onto the EP2 via Leica M adapter. Wide-Open At F4: F1.5: F4 The ZOMZ J-3's are a bit softer than the earlier KMZ J-3's, at least in my experience. This 1967 J-3 is perfect glass, and is better than many 1960s J-3's that I have used.