Originally posted by robgo2 FA43 is plenty sharp at F1.9
This shouldn't be a shocker, the lens is only f2.
50 1.4 is plenty sharp at f1.4, but you need to get the damn thing in focus.
Buy the lens with the focal length you want. 43 is going to be a short telephoto, not good for traditional portraits, better for environmental portraits. 50 is going to be borderline for traditional portraits, and the 55 is going to be ideal for that.
If this is your motivation, realize all three lenses have killer bokeh, colour, and sharpness. It's the focal length you need to think about.
If it's just about "sharp wide open", you should just set the AF adjustment on your FA 50, and shoot it at F2. Other then some differences in bokeh rendering and focal length, the 50 and 43 will render very similarly in this particular circumstance.
FA 43 is best for shooting stopped down for extreme sharpness. Nothing particularly special about this lens wide open IMHO.