Binoculars — The Space Between
Movies get it wrong
In the movies, you see somebody pick up some big heavy old binoculars and look through them, and then the movie shows you what they supposedly see.
It's a sort of dumbell shape, like two circles side by side, and maybe overlapping a little. Pinched in at the middle, where a person would actually see the full height of the image. Oh, so wrong!
It makes you wonder if the folks who made the movie have ever looked through a pair of binoculars in their whole life.
That is not what you want it all. You want to see one image. Like you do with your eyes in real life. And that is exactly what you will see when you get the two barrels of your binocular set at the correct distance apart. That is, when you get the interpupillary distance right.
Customize your new binoculars
This tip assumes you have already set the eyecups to work for your eyeglasses status. (Twist eyecups out to longer position if you don't wear eyeglasses; twist them down to shorter position if you do wear eyeglasses.
Now you're ready to set the proper distance between the two barrels of the binocular. The goal is to have the center of the left and right eyepieces directly in front of the pupil of your left and right eyes.
But people's eyes differ. Some are wide spaced and others are closer together. So binoculars let you adjust the interpupillary distance to match the distance between the pupils of your eyes.
Set the interpupillary distance
Here's how to do it. Don't worry about focus just yet. All we're doing right now is setting the distance between the two barrels.
Hold the binocular up to your eyes and bend the hinge, moving the barrels closer together or farther apart until the two images become one circle.
When you see one circle, you have the interpupillary distance set correctly. That's all there is to it.
Now you're ready to focus your binocular. If you find that you can't focus both eyes at the same time, you may need to set your diopter.