"Instead of approximating a partial-diff, we can simply plug-and-chug numbers of assumed human motion velocities. Multiply the shutter interval by your approximated motion. If this number is greater than your GSD, your image will not be critically sharp. It's that easy."
OK, I understand everything up to "Instead of"
Can anyone who actually does understand this PLEASE give me a ballpark guesstimate of whether it is humanly possible for an ordinary coffee-drinking mortal to get an acceptably sharp shot of a person standing still about 3-5 meters way out of a 33MP eMotion75 back with an 80mm lens on a Contax 645 or similar camera?
If yes then what is the slowest shutter speed I should drop my Contax 645 down to if I want to not take too great a risk that the eyes of the person will look like porridge?
By "acceptably sharp" I mean that if I print the image at 300dpi edges of eyes, hairs and contours of lips are more like lines than blobs.
And to complicate matters even further, what is the minimum shutter speed you would suggest if the person is moving at a walking pace across the frame at a constant distance from the camera?
Maybe like most others reading this even I can figure this out with film but have more trouble doing same with digital.
The reason that I am asking is to try and figure out if I really can hand hold this beast or if I need to invest (which I really don't want to do) in a lower rez DSLR to take over when I want to go off tripod.