What is a Pentax FA31Ltd?
It is a smallish lens that gives 31mm FOV (not 35mm) and its associated ease/difficulty in designing one.
On my travels, I'm out at 4am-5am and back in the hotel room at 10pm, often on foot for long stretches, over a whole week.
That lower encumbrance certainly helps. (esp when there will be another 3 lenses in the bag)
The 31mm FOV is unique certainly, an "in between" of a classical 28mm and a 35mm.
It allows this reportage style of coverage of the human condition.
and yet, at a switch, that wideness is pretty good for landscape as well
At more open apertures, there is a good consistency to the bokeh (in most cases) and often, the good separation between subject and bkgnd.
Sharp, sharp and more sharp is the emphasis nowadays.
Often, I don't even bother with sharp edges when shooting at larger apertures (the subjects are often not even placed there)
If its stopped down, most lenses are good at f8, f11.