I know this is an old thread, but hey, how is your experience with Nikkor 50mm f1.4 AIS. having 50mm f1.8, is there any reason I should try 50mm f1.4?
Years ago I bought a 50/1.4 AI and found it was not as sharp at f/2.0 as my 50/1.8 AI was wide open. Those who know more about optics and these lenses may comment. Today my guess is the 50/1.4 AI exhibits more spherical aberration at large apertures than the 50/1.8 AI. There is an soft veil over the image with the 50/1.4 AI and AIS at f/1.4~2.0. With today's high ISO performance DSLR(s) I see no need for a 50/1.4's extra speed over a 50/1.8.
My favorite 50mm lenses today are my 50/1.8 AI and 50/1.2 AIS. Some claim the 50/1.2 AIS is the sharpest 50mm Nikkor at f/2.0. If true I’m not sure this really matters. The 50/1.2 AIS has a buttery smooth focus feel. The 50/1.2 AIS exhibits slightly more barrel distortion than the 50/1.4 AIS and has hard vignetting in the corners at f/1.2 to f/1.4~. I would not spend the money I did on the 50/1.2 AIS again.
I also own a 50/1.4 AIS but it's aperture blades are oil fouled. It's been cleaned twice and the problem returns so it needs a full strip and re-lube. I've never gotten around to it. I intended to sell the 50/1.4 AIS after buying the 50/1.2 AIS.
Dave