This is one of those settings that mystified me for years but I read through a pretty straightforward write-up on diopter adjustment and have been on the straight and narrow ever since.
Good binoculars will have two adjustments, your focus wheel, which lets you focus in on the bird or other creature that you’re observing, and the diopter ring (or diopter adjuster). The diopter is something that you basically just set and forget about but it’s really important to making your binoculars function well for you.
Our eyes don’t focus exactly the same at the same distance so this adjustments lets you account for that difference. Once the diopter is set, both barrels will be in focus for you as you use the main focusing ring.
The diopter setting will be individual to you (no two eyes are the same) and this is why it becomes hard to share binoculars (among other reasons….like wow there’s a cool bird, oh let me see…no get your own binoculars…).
Anyway, going through these steps allows you to set the focus of each eye separately. First you’ll focus your left eye using the main focus ring, then you’ll focus the right eye using the diopter adjuster. Once set, this will then give you maximum sharpness when using the central focusing ring as you hone in on that cool bird or butterfly or wildflower or whatever.
So here we go…..To set the diopter ring and focus adjustment for your eyes, you go through these easy steps:
– First, find the diopter ring on your binoculars and put it into position so that you can adjust it. On some binoculars, the ring clicks into an “up” position and you can feel it click through different settings as you turn it. On others, it’s a ring that turns. The photos here show both styles and there may be others too. In any case, set the diopter ring to the Zero or center setting so you’re starting there.
– Next, pick something on a wall about 30 feet away that you will use as the thing you focus on. Using your lens cap, cover the barrel that the diopter ring is associated with (usually the right barrel). If your diopter ring is located in the center, then cover the right barrel.
– Keeping both eyes open (no squinting), adjust the central focus knob so the object that you’re looking at (about 30 feet away) is as clear as possible for your left eye. Leave the central focus knob in that position. Your left eye is now set.
– Next, move your lens cap to the left barrel to cover up that side. Now you will focus your right eye using the diopter ring. You will not move the central focus at all. Looking through the binoculars (keeping both eyes open), focus on the object that you used before and adjust the setting of the diopter ring until the focus is sharp for your right eye. On some binoculars, you’ll need to unlock the diopter ring in order to adjust it, just look at your manual to see how it’s done. Often, you just lift the ring and turn it left or right and then restore it to its regular position.
– Lastly, take the lens cap off and see how things look using both eyes. After going through these steps, you should be able to focus well using the central focusing at any distance.
This wraps it up for now on our Binocular FAQs. If there are other topics that you’re interested in, let me know 🙂