An Ai-S mount pancake lens, introduced with the Nikon EM. There were two versions of this lens. The first version is all black. The 2nd version has a chrome index ring. I tested the black version. The focus ring is small compared to the normal 50mm lens, but it feels like a Nikon lens. At f1.8 the lens shows some vignetting and contrast is a little soft. Vignetting is gone by f4. Contrast firms up at F2.8. Sharpness is excellent from f2.8 up. At f4 and F5.6 it is tack sharp. No noticeable fringing. Bokeh is smooth and stays smooth even at f16. It would work well for video.