Last updated on May 10th, 2023 at 10:51 pm
Birdwatching is almost impossible without a birding binocular, whether you’re out in the wild or trying to get a closer view of the backyard or garden birds in your area. However, many birders encounter several birding binocular problems and wonder about how to fix them.
The most common birding binocular problems include blurry, distorted, dull, or dark images. Many birders don’t experience the natural colors or finer details, some bins get foggy, and eye fatigue is common. Also, live viewing, scanning, and the spotting are often wobbly.
1. The Images Are Blurry or Distorted
Presuming your birding binoculars are relatively good quality and are in impeccable condition, blurry or distorted images are usually due to the following issues:
- Focus
- Vignetting
- Heat shimmer
- Diopter adjustment
Focus is a dynamic characteristic of any birding binocular that you must constantly change to improve viewing or image clarity.
However, heat shimmer is a circumstantial and topographical factor that you can’t do anything about other than avoiding unusually high magnification.
Hot air currents rising across marshes and fields can create significant distortion when you use a birding binocular with the following magnifications:
- 20x
- 15x
- 12x
Vignetting is fading or blurring around the edges of your view.
But the image may also be a bit darker than it should be, which can be due to improper eye relief and exit pupil.
Likewise, diopter adjustment issues are common if you don’t calibrate the two barrels or tubes and lenses.
How To Fix
Here’s how you can prevent vignetting while using a birding binocular:
- Adjust the binoculars’ eyecups by extending or retracting them to find the optimum eye relief and exit pupil.
- Whether corrective or protective, birders wearing eyeglasses should retract the eyecups to account for the extra gap.
Birders wearing corrective eyeglasses, not lenses, must use binoculars with longer eye relief.
So, if your current pair offers 15 millimeters, perhaps 20 millimeters will be more suitable.
Diopter adjustment is an essential calibration for all modern birding binoculars.
The knob or dial can get inadvertently moved even if you have adjusted it once.
This means you need to adjust the diopter to set or restore the focal and magnification balance of the 2 objective lenses to suit the slight vision discrepancy between your left and right eyes.
Here’s how you can calibrate the diopters:
- Select the ideal position for the adjustable eyecups to align your pupils perfectly.
- Check if you have an extendable central focus knob or a diopter adjuster on one barrel.
- Close the lens cap with the diopter adjuster (usually the right eye) on the barrel.
- Look at a point at a fair distance through the left lens and adjust the focus for clarity.
- Close this lens cap, open the other and look at the same point with your right eye.
- Use the diopter adjuster or extended focus knob to attain the same clarity on this eye.
Don’t forcibly close one eye as you use the other to calibrate a diopter because that leads to squinting and distorted vision.
2. Low-Light Images Are Too Dark
A bin with very high magnification reduces the field of view and the quantum of light passing through the lenses.
This problem worsens if the objective lenses’ diameter is small or midsize. Both these issues combine to reduce the exit pupil to a suboptimal size.
Here’s how to calculate this:
- An 8×42 binocular has an exit pupil size of 5.25 millimeters.
- Your normal pupil size is around 7 millimeters in low light.
- The exit pupil is smaller than yours in dark conditions.
- A 6×42 or 7×50 binocular offers a 7-millimeters exit pupil.
How To Fix
You’ll need to buy a bin that performs well in low-light conditions.
Also, always test a binocular in dark or low-light settings before buying, as brightly-lit shops won’t reveal exit pupil issues.
Human pupils are around 2 to 3 millimeters in bright light, so bins won’t pose a problem in that regard.
3. The Colors Aren’t Natural or Clear
Inexpensive birding binoculars don’t often deliver the natural colors and clear details due to a few shortcomings, including the following:
- Poor color rendering
- Inferior quality lenses
- Bad optical elements
- Subpar lens coatings
- Absurd magnification
- Field of view problems
How To Fix
Color rendering or lens quality is an inherent issue that you can’t fix yourself.
If your binoculars are clean and undamaged, the colors and details you view are the natural capacities of that model in different settings.
The only way out of this problem is to buy a better birding binocular.
4. The Binoculars Are Often Foggy
Most birding binoculars can get foggy on the outside due to condensation. But some bins are also foggy inside.
That’s due to trapped air and moisture inside the barrels, which you can’t simply wipe off using a lens cleaner.
How To Fix
The solution is anti-fog binoculars. These bins are purged with nitrogen or argon, preventing fogging inside the barrels.
Some birding binoculars have anti-fog coatings outside the objective lenses, so they won’t have a condensation problem even when the conditions aren’t pleasant.
5. You Can’t Find or Follow the Birds
The most common birding binocular problems that may prevent you from finding and following birds include:
- Limited angle or field of view
- Extremely high magnification
- Focus or diopter adjustment
- Improper eye relief or exit pupil
How To Fix
Here are the solutions based on the problem you detect:
- Calculate the field of view at 1,000 yards if you don’t have the information available.
- Check the angle of view on your birding binoculars, which could be 5°, 6°, 7°, etc.
- You may use trigonometric integrals and gamma functions to calculate the field of view.
- Multiply the angle of view by 52.5 instead of using the ISO 14132-1:2002 way.
- The effective field of view for 6° is 315 feet, and 7° is 367.5 feet at 1,000 yards.
- If the field of view or magnification is fine, adjust the focus or calibrate the diopter.
- Adjust the retractable cups for eye relief and to correct any exit pupil alignment issues.
6. You Experience Eye/Ocular Fatigue
Ocular fatigue isn’t unexpected if you spend hours on your birding binoculars. But sporadic and unexpected eye fatigue may be due to the following problems:
- Inappropriate eye relief
- Inaccurate eye cup position
- Small exit pupil in a situation
How To Fix
Adjust the eye cups for adequate relief.
Otherwise, your eyes and brain will constantly try to adapt to the unusual viewing experience to process the images accurately.
Ideally, you should adjust the bin’s hinge to suit your interpupillary distance and eye cups for every new session.
If your eye fatigue or other ocular problems are due to the exit pupil, lenses, or coatings, you must get a new bin or consult an ophthalmologist.
7. Live Viewing Is Wobbly or Unstable
Wobbly live viewing or unstable images are mostly due to extreme magnification unless you gradually learn how to scan and spot, which is essentially birdwatching.
High magnification is a common problem when you try to spot and track swift small birds that rarely stay stagnant.
How To Fix
Any wobbliness during hand movements and other motions will likely subside with practice.
But a very heavy birding binocular or one with absurdly high magnification can still be a problem.
A tripod adapter is a practical solution, and a spotting scope is better for long-distance birding.
See also our article on how tall a tripod you need for spotting scopes.