I have the 1.4 Ais, the MF 1.8 H.C, and my wife's AF 1.8. Tested them all at the same time, on 100 speed chromes, tripod, cable release, mirror lockup, DG-2, two bodies and two rolls, all F-stops up to F8, shot at near middle and far-ish middle distances. At wide open, the 1.4 is better but not by much over the AF 1.8, the center is sharper on the 1.4 but the AF is more even over the whole frame. At F2, the 1.4 is clearly better, bokeh is clean and plane of sharpness extend over the whole frame, very nice overall look. The AF 1.8 and the old H.C 1.8 were pretty even at this point, the H.C had a bit 'different' signature to the bokeh, but sharpness was nearly the same. At F4-5.6, the differences between all lenses was so minute that I had to consult the notes to figure out which lens was used. I use and interchange between them all the time, taking the 1.4 when I need more wide open performance and the weight issue is minor, taking the 1.8 when I need the weight savings and less chance of a *critical* need for wide open performance. The AF is currently in 'need to be repaired' status, needs a good cleaning and perhaps a new mount.