Hi, I’m Bill Thompson, III, with your newest episode of Birding Basics and Beyond. Today I want to talk about birding binoculars.
A lot of people will get an awesome new binocular, tear it out of the box and start using it without ever realizing how to properly use it. On the most basic level, using a binocular is pretty simple: You put the binocular up to your eye and look through it to see stuff better. The binocular magnifies the image, which helps you to see more detail on the birds.
But believe it or not, there’s a little more to using your binocular properly. If you’ve ever experienced, tired eyes, a headache, or even nausea after using your binoculars on a full morning of bird watching, you’ll want to hear this important tip.
Looking at a binocular, you’ll notice two focus wheels: You’ve got your primary focus wheel, typically here in the center, which is what you turn to adjust the focus between looking at, say, a chickadee or warbler in the branches just a few feet away, versus looking across a lake or up in the sky at a soaring hawk or eagle.
Your second focusing wheel might be located here on the eyepiece, or possibly over here with your main focus wheel. This second wheel is called the diopter. The diopter adjusts the focus of the right barrel of your binocular to compensate for the visual acuity of your two eyes. Almost everyone who uses binoculars needs the added focusing flexibility of the diopter since most of us have eyes that are not exactly equal in their focusing ability.
Adjusting your binocular’s diopter is actually very simple. Here’s what you should do. First, find a stationary object, such as a stop sign, bird house, or whatever, about 50 yards away, and put your binocular up to your eyes with your right eye closed. So you should be looking only through the left barrel of your binocular. Now, adjust your main focusing wheel to the left or right so that the stationary object is perfectly clear for your left eye. Now, close your left eye and open your right eye, looking only through the right barrel this time. Don’t touch the main focusing wheel! Instead, you want to adjust your diopter wheel so that the object you’re looking at becomes crystal clear for your right eye. Once you’ve got it focused, open both eyes and look through both barrels. The stationary object should look perfectly clear.
From now on, your binocular should be set for your individual eyes. You should never have to adjust your diopter again; that can stay set. Instead, during your day-to-day birding, adjust only your main focusing wheel.