David J. Littleboy wrote:

The best thing to do is to test. For each focal length,
for each f stop, shoot a series of images of a scene
with both near and far detail at various distance settings
on the lens starting at infinity. For each focal length/f
stop combination, record the closest distance that you
find the detail at infinity to remain acceptable.

Since it's digital, all it costs is your time. And even then,
not much of that since you don't have to scan.

Got it. I'll set up a 20-meter tape measure in my back yard
and put up letter-sized paper sheets labeled with the distance
at 1-meter intervals. That should do it. Thanks.