A few weeks ago brocknroller mentioned somewhere here that his Zen focuses better going from near to far (or far to near--I can't remember). Intrigued, I tried out a couple of my bins as well. Sure enough, some focus a bit better going one way rather than the other. It's very slight, of course, but going in one direction really "snaps," going the other direction leaves the feeling of a slight diopter misadjustment. Evidently there is often a tiny amount of focus slop that differs between the barrels. In effect, one barrel lags behind the other. The diopter can only be set to correct this going in one direction. DOF must also play a role. So far, I've noticed it on a Zen, Zeiss, and Leica, so quality may not be too much of a factor.
Of course if the diopter were slightly readjusted the best focus direction could easily be reversed. So I'm thinking about readjusting diopters on my affected bins so that they focus best in the same direction (near to far or vice versa??). Saves the bother of trying to remember which way to come to focus on each bin.
Check it out. It sounds like splitting hairs but one way I get a real "pop" and the other way sometimes feels a little vague.
This might be why Swarovski now makes a big deal about their "completely tolerance-free" focus mechanism on the Swarovision. Assuming it really works, you should get a solid "snap" going either direction.
Any thoughts on this?
Mark