Interesting comments Derrel. I'm going to do some bokeh testing on my 85mm, 135mm lens, and 70-200mm lens just to see what I get.
try some things that really,really SHOW bad bokeh: chain-link fencing, picket fences, shrubs, and light coming in from behind trees or large hedges, etc, and also high-frequency stuff, as well as LOW-frequency, large-ish stuff like playground jungle gyms; poles; cars and vans,etc.
See if the bokeh has
double-lining on things like gladiola stalks, or fences, or window frame edgesm, stuff like that. Big problem with some of the old Zeiss designs.
RE: 85mm lenses. Nikon 85mm f/1.8 AF or 1.8 AF-D. The KING of purple fringing on high-contrast things like tree branches, phone lines, edges of things against bright sky. Cheap. Old design. NEWER 85mm 1.8 AF-S G...perhaps THE SHARPEST, highest-testing 85mm lens for high-MP Nikons. Sterile rendering. Extreeeeeeemly good optics, perhaps the best lens under $4,000 from Nikon. VERY sharp edges, even at f/2.2 or f/2.5. Low spherical aberration, very modern, well-corrected, tests out as one of the absolute best primes on 36 MP Nikon D800 or D810.
Buuuut....the real portrait lens is the older, 85mm f/1.4 AF-D Nikkor, also called, "The Cream Machine" back in the early 2000's. Optics? Light fall off at the edges, not that sharp at the edges, much sharper in the central core of the image. At wide apertures, edges are softer than the central zone, by a good bit. IOW, portraits of one or two people look gorgeous, right off the memory card...natural subtle vignetting, softer outer area that does not distract, sharp in the center; spherical aberration has been allowed to remain to a degree, so the OOF areas are freaking gorgeous. Does not "test out" on a test chart like a Rokinon. And yet, it is a spectacular lens for pictures of people.
You might not see much vignetting on "some" lenses. And if you import with lens profiles/corrections applied, you might not see "any" light fall-off at the edges. And with some new cameras, in-camera JPEG will apply vignetting control. On longer tele with narrow angles, light fall-off is often pretty minimal. On APS-C camera, light fall-off is often NOT EVEN there,ever, sicne the lens "sees" only that 29mm dia. circle in the center of the lens's projected image.