Binoculars with a central control focus also include a diopter that allows you to adjust for differences in vision between your eyes easily.
⦁ Cover the right-side lens with a cap and focus the central control on a distant object.
⦁ Next, switch the cap to the left lens and focus the diopter control on that same target.
⦁ After that, leave the diopter as it and use the center control for focusing.