Calibrating binoculars adjust your binoculars specifically to your eyes. You can do this on your binoculars if you have a diopter, which is another dial (not the focus), that is usually near the right or left eye cup. Adjusting the diopter allows you to take any differences between your left or right eye into account, which is especially important if you are nearsighted.To calibrate your binoculars, first find an object about 30 feet away. Then, look through the binoculars, close the eye that has the diopter, and focus the binoculars with the focus knob. Then, open the eye you had closed and close the opposite eye while still looking at the same object. You now adjust the diopter (not the main focus knob) by turning it either left or right to bring the object into clear view. Now, your binoculars will be calibrated to your specific eyes.