I'm starting to get confused now. As I recall it, the wider open your lens, i.e. 2.5 the faster your shutter speed, the faster your shutter speed the less camera shake. Sure at 2.5 and close to your subject you do reach the place where the slightest wobble toward it will "blow" the shot but conversely the slightest wobble away still keeps you in the game. I'm going to tell something some nikonites may find ghastly, very un-PC, but 43 years ago after a stint as a vegetarian I moved from the big city into the country and rented a big farm house. The farmer was very happy if I got rid of rabbits, and geese in season: geese eat a huge amount of grass rabbits eat less but their burrows cause hillside erosion. I decided since I was taking their lives, plucking and skinning and cleaning them, I could now eat meat as karmically speaking I was taking full responsibility. Soon I moved on to bigger guns, wild boar, goats and deer. Then I got a telescopic sight for more precision at longer ranges but even after I had sighted it in on targets I was finding I was often missing the shot: I preferred a clean kill you see. We made new friends up there and one was a deer hunter to whom I explained my problem and the answer he gave me, I think is relevant to this topic.
He said, don't just aim your crosshairs on the region of the heart, or brain, but focus on a particular tuft of fur and aim at that, then hold steady until you can see a tuft of fur, then one or two individual hairs hold steady then squeeze the trigger/shutter.
Lastly, I have my hand cupped around the focus ring and am constantly tweaking: either I am focused a smidgeon beyond the subject of a smidgeon this side and then I bring it into focus and snap!
With a digital set your ISO high enough so that at f2.5 your shutter is at at least 1/90 sec. There should be no excuse for not being able to move further away or closer if needs be (unless you are in a wheelchair like me,) I have an old 135 /2.8 ai too, heavy as hell but cheap nowadays and what a lens! As for talk of modern screens not being good for manual, I cannot say, I don't own a 3200/3300 I only have a D200 and more lately a D610 and with live view I can't go wrong: incidentally with manual lenses I use the back screen (matte) and swing the helicoid in and out until my subject looks most "there" plus, I never play about with portraits slower that 1/125 if I can help it, a good portrait is fleeting: now you see it now you don't. And it is not about "sharpness" IMHO but capturing the inner being.
Hope this long ramble helps.
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