Let’s get one thing straight, even the best binoculars can’t give you the expected results if not adjusted properly. The worst case scenario can be double vision that gives you disproportionate images. If you’re also facing the same, this article will be your ultimate guide on how to adjust binoculars with double vision.
In most cases, the issue is with the IPD (interpupillary distance) where you have to adjust the center diopter. If one of your binocular lenses comes with an individual diopter, adjust the other first. After that, you can adjust the independent one, and then adjust both together parallelly for the zoom or clarity.
Let’s understand how this happens in the first place and what else you can do to resolve it.
What Is Binocular Double Vision?
Binocular double vision is an issue all experienced binocular users may face at times. Most of the time, it only happens when you have both eyes open on both lenses of binoculars. You can use either eye just fine with sharp image quality in front. However, when you’re to use both eyes, sometimes the binocular fails to align both images from the lenses into one. This misalignment is often a result of the prisms on either lens pointing in slightly wrong directions, aka Collimation. Hence, you’ll see one image separated into two misaligned images.
You can relate this issue to a neurological medical condition like binocular diplopia.
Possible Causes Of Binocular Double Vision
There are three types of binoculars: monoculars, Porro prism, and roof prism. Getting double vision happens when either of the prisms misaligns with another, distorting the way for the lights to come in. You can get four types of distortion in the visible picture through the lenses where the secondary image (left or right) will go off the level. It can go downwards to the right or left, or upwards with the same pattern. Binoculars double image can happen for a few reasons such as:
- Manufacturer’s defect: You might receive a binocular from the supplier with double vision right out of the box. It happens in the assembly part of making the pair of binoculars in the first place.
- Shock or bumps: If you get your pairs of binoculars to bump into anything that can shake the internal mechanism, you may get double vision. It can happen when you keep them on the floor while hunting or keeping them without a hard case.
- Aggressive adjustment: Binocular focus problems also can occur if you rotate the diopters and dials aggressively while they won’t rotate without force. Remember, they’re not to be dialed with force, rather gently up to the end.
How To Adjust Binoculars With Double Vision
When you have your collimation, or the prisms within the binoculars aligned wrong, fixing it has a complicated process. Nonetheless, we’re going to discuss how to adjust binoculars with double vision anyway if that helps you out.
Try the legit way first
Before you get your hands dirty and start taking your binoculars apart, check for warranty first. If you’ve just received it from the supplier or bought it a few months ago, check if you’ve got warranty left. With a warranty still in action without physical damages, send it out to the manufacturer and claim your repair.
Apart from giving you a professional repair for the binocular, that’ll also keep the warranty intact. Otherwise, if you get your hands inside the protective layers, the warranty will surely be void.
See If a Lens Adjustment Does the Job
If you take your binoculars to a repair shop, the first step they’ll take is checking for a proper IPD. The interpupillary distance (IPD) is the distance to your pupils from the center adjustment diopter on the binoculars.
To test and fix that, you’ll have to make a few precisely measured adjustments. First, locate which lens has the individual diopter (usually it’s on the right lens, right next to the eye cup). Close your right eye or eyepiece, and adjust the left lens with the center adjustment dial as you do usually. Once that’s in place, close your left eye and adjust the right lens with the dedicated diopter.
Now that you have them both adjusted, see if they’re showing a single image properly with only a single object. If not, try to adjust them both with the center diopter at the same time. If that doesn’t seem to work, take one step back and adjust the front lenses to be sure. This step should fix the double vision if the problem’s with the lenses only.
Fix the binocular double vision (the hard way)
If lens adjustments don’t cut the issue, and you don’t have a warranty, you have to get inside. You’ll have to adjust either the prisms, or the front lenses by adjusting the screws intended to do the job. Let’s see how the process works and how you can do it yourself:
Locate the adjustment screws
There are protective layers on all four sides of the lenses (2 for each) and you have to peel them all apart. But before that, be sure to check if all the adjustment screws are hidden under a protective layer. If they’re exposed to the bare surface, or just secured with glue, you’re lucky. Take a small size screwdriver (usually 0.050 size or so) and start working.
Expose the screws
If you can’t find the screws on the surface, know where they are. You can find the location in the user manual or the internet, depending on the model you’re using. If you cannot find them, take an exacto knife, peel the protective layers on all four sides, and manually locate them. Once exposed, you can do the adjustment both at a clear night or daytime.
Target your objective and adjust one lens
All four adjustment screws drive the unparalleled picture in its own direction. Therefore, you must have a clear objective in front of you to do the adjustment. And you’ll need a solid base (works best with a tripod) to set the binoculars up for a steady, proper image. If you’re doing it at night, pick the brightest star as your target. Or you can draw a + (plus sign) on a piece of paper and set that at 160-200 yards distance.
Aligning the objective
After getting your target ready, adjust one lens that’s above the flat-line (usually left) to see the target clear. You can also defocus it all the way to make an outline to fit the next picture into it to eliminate distortion. Close your left eye, look through the right lens, and rotate the focus knob until the target becomes defocused. Don’t forget to put the binoculars onto a firm place such as a tripod to keep the picture steady.
Making the adjustments
Once you have the objects in place (500-700 ft away) with one defocused, take an appropriate screwdriver (usually 0.050) for minor adjustments. Make sure it’s from a good manufacturer to avoid a poor adjustment that could damage the screw heads. Start by rotating the screw at the far bottom right corner lens slightly and see how the second picture acts.
If it starts to fix towards the first picture, which is the defocused one, things are going well. If not, take a step back and try with another screw and so on, until you get the picture aligning. For a horizontal misalignment, you need to make horizontal adjustments, or you’ll do a vertical adjustment to get the image correct.
If you’re seeing double through binoculars and wanted to fix the issue by yourself, there you have it! Now you know how to adjust binoculars with double vision without taking it to a professional. This guide will especially be helpful if you get into an issue while in the middle of your hunting trip. If your binocular breaks on double vision, you can fix it yourself within a few minutes! All you need to carry are small tools like a prier and a little screwdriver with you.