This compensates for any vision differences between your left and right eyes.
Once set, note the number on the left and right binocular tubes that the index mark on each eyecup is lined up with.
With the display focus and diopter adjustment set to these positions, you should be able to obtain sharp viewing of
objects at any distance by simply adjusting the center focus knob while you look through the binocular. There is no
need to re-adjust the display focus or diopter adjustment, unless you share the binocular with another user, or if your
eyes become tired over a long period of use.