I know the 1.4 is nicknamed the "cream machine" but does that smoothness translate to any other apertures? Is there a difference between the 1.4 and 1.8's micro-contrast or sharpness at smaller apertures (i.e. f4 or above)? Any other reasons to prefer one over the other?
Christopher, here are two tests of both lenses made under completely identical test conditions:
1.4 / 85 AF-D:
https://www.opticallimits.com/nikon_ff/538-nikkorafd8514ff
1.8 / 85 AF-D:
https://www.opticallimits.com/nikon_ff/622-nikkorafd8518ff
And here the assessment of B. Roerslett of both lenses:
http://www.naturfotograf.com/index2.html
I own and use regularly the 1.8/85 AF-D, the 2.5/105 AI-S and the AF-D 2/105 DC.
The 1.8/85 AF-D is an excellent lens, with an outstanding price-performance ratio. Its strengths are
- already quite good sharpness at open aperture (better than the 1.8/50 AI-S and 1.8/50 AF-D), but with less contrast ( a bit soft, like the 1.8/50s; that is typical for most Gauss type 1.8/50 and 85 lenses)
- very good to excellent sharpness and contrast from 2.8 on stopped down
- very even performance over the whole frame (much better than the 50 Nikkors)
- very fast and accurate autofocus
- good manual focus
- very effective lens hood, no problems with flare
- compact and relatively light
- robust: my 1.8/85 is serving me very well without any problems for 23 years now.
- outstanding price-performance ratio.
Concerning the bokeh of this lens: I have never had any problems with it. It is certainly
not worse compared to the 2.5/105 AI-S (and have you ever heard someone complainig about the bokeh of that lens?). The 1.8/85 AF-D has even a (generally more "bokeh-friendly") 9 blade aperture, the 2.5/105 has a 7 blade aperture.
In direct comparison the AF-D 2/105 DC is optically the best of these three (portrait) lenses (it is a league of its own). Followed by the AF-D 1.8/85 and the 2.5/105 AI-S (both are very close in performance).
Best regards,
Henning