What is eye relief in binoculars?
Let me guess, you’re looking to buy a pair of binoculars but you have no idea what some of the features mean?
So now you’re wondering if eye relief is something you should be looking for. But really you have no idea what it even is!
I know the feeling.
That’s why I’ve written his guide all about eye relief in binoculars.
We’ll discuss what eye relief is, if you need it, and what to look for if you do.
Sound good? Then let’s get started.
What is eye relief in binoculars?
When you look into a set of binoculars you’ll only get a great image quality if your eye is the ideal distance away from the eyepiece.
That distance is known as eye relief.
It’s the maximum distance your eyes can be from the oculars (the smaller lens you look through) while allowing you to see the entire field of view
Think of a hunter with a rifle. Notice how they leave a gap between the scope eyepiece and their eye?
They need a long eye relief that allows them to see through the whole field of view, but also a buffer space for gun recoil.
Birdwatchers are a little different. You’ll be holding the binoculars close up to your eye.
The eye relief is then that small bit of space between where your pupil stops and the ocular lens starts when the eye cups rest on your face.
How important is eye relief in binoculars?
Eye Relief is usually not an issue for binocular users unless you wear glasses.
Although it may also be an issue if you have very deep-set eyes.
That’s because your glasses prevent you from getting your eye as close to the lens as possible.
And so if you wear glasses you’re at a disadvantage because your glasses prevent you from getting the eye cups in close.
That cause two problems for you:
1. Reduced Field of View
2. Increased peripheral light
Let’s look at each issue.
Eye Relief and field of view
When your eye is the ideal distance away from the lens you’ll see a great image.
When it goes back further than this, you start to get a reduced field of view. That means that you’ll miss out on a part of the binocular image and ultimately potential bird spotting.
So no matter how good you’re binoculars are, you’re going to get short-changed each time you use them.
Eye Relief and Peripheral Light
Peripheral light is the small amount of light you can see at the side of your eyes when you have your eye cups up close.
The closer you can get the cusp to your eyes, the less peripheral light you’ll see. Wearing glasses increase the amount of peripheral light and vision you see with binoculars.
Unfortunately, when you wear glasses you can’t prevent this issue, but you can reduce its impact.
Adjusting the eye relief on binoculars when you wear glasses will help to cut down on this issue. You’ll be able to focus better with less distraction from your peripheral vision.
Should you wear glasses with binoculars?
So you’re probably wondering if the logical step is to stop wearing your glasses when using binoculars.
If you only use glasses for magnification, you’ll be able to use your binoculars without them.
The problem with that is if you have prescribed glasses for conditions such as astigmatism. Your vision will likely be poor without your glasses on.
But don’t worry if you need to keep your glasses. Binocular designers have figured out a clever way around this issue.
Eye Relief Feature in Binoculars
So you may have guessed that the eye relief feature of glasses is there to help the binoculars adjust for glasses wearers.
Any good-quality binoculars will have an eye relief feature. I’d question the quality of the binoculars if they don’t.
The eye relief feature won’t affect those who don’t wear glasses but may make the eye cup fit more comfortably.
Let’s look at the two types of Eye Relief
Short Eye Relief in Binoculars
Short eye relief is anything under 13mm.
Birdwatchers don’t specifically go looking for short eye relief, that’s more of a feature on hunting scopes.
Short eye relief is a binocular spec only suitable for anyone who doesn’t wear glasses.
If you wear glasses then eye relief is a spec you need to consider when buying binoculars. Then you need to avoid choosing any model that has a short eye relief spec.
That’s because even the thinnest of glasses will result in you needing eye relief over 13mm. And ultimately you’ll always miss out on part of your FOV.
Long Eye Relief In binoculars
Long eye relief is anything over 20mm.
Birdwatchers with glasses do need to go looking for binoculars with long eye relief.
That’s because binoculars with long eye relief will adapt to suit pretty much all glasses regardless of their thickness.
The ability to adjust the binoculars that little bit further will be the difference between seeing the whole field of view or missing out.
And when we’re talking about dropping hundreds if not thousands of dollars on binoculars, the last thing you want is not to get the full use of them.
What is a good eye relief for glasses wearers?
You may have noticed that eye relief in binoculars can vary anything from 5-24mm.
If you wear glasses ideally you want binoculars that have an eye relief of at least 16mm.
I would suggest looking for a spec of around 18-19mm just to be safe.
Most glasses wearers will be safe using binoculars with an eye relief of 20mm+. The issue is that these models are often expensive high-end options.
Really it will depend on the thickness of your glasses.
If the eye relief is short on a set of binoculars you may be able to reclaim some space by flipping back the padding or retracting the eye cups.
Is Eye Relief the same as exit pupil?
The exit pupil and eye relief are not the same measurements.
Exit pupil is the diameter of light leaving the lens. When closed this number is to the size of your pupil the brighter the image will appear. And so a larger exit pupil will always give brighter images than a smaller exit pupil
This is measured in millimeters (mm) and is calculated by dividing the objective lens by the magnification. So an 8×32 binocular will have an eye relief of 32/8 = 4mm.
Your pupil size changes during the day and night. For bird watching a larger exit pupil will help if you use your binoculars in low light conditions.
The confusion with eye relief comes from the fact that the exit pupil determines the eye relief for binoculars. Also, some brands like Zeiss will list the eye relief as the ‘exit pupil distance’ and the exit pupil as the ‘exit pupil diameter’.
The exact eye relief distance is determined by the point at which the exit pupil size reaches your eye.
Are 8x or 10x magnification binoculars better for eye relief?
Eye relief changes with magnification.
That’s because the exit pupil changes with magnification. So an 8x binocular will give a larger exit pupil size than a 10x (based on the calculation above).
A larger exit pupil size allows for a longer eye relief distance.
You’ll notice that the 8x version of any binocular model will give more eye relief than the 10x version. Usually, this is around a 1-3mm difference.
Let’s take a look at a few examples:
The 8×42 version gives 19.5mm eye relief whilst the 10×42 gives 18mm
The 8×32 version gives 16mm eye relief and the 10×32 gives 14mm eye relief.
The 8×42 model gives 19mm eye relief and the 10×42 offers 16.5mm eye relief.
You’ll see from these examples that you won’t be restricted to using a certain magnification to allow for eye relief. However, you’ll have more success getting a larger eye relief in a binocular with 8x magnification.
Binocular magnification is all down to personal preference. But you may need to shop around a bit more if you’re a glasses wearer who prefers a 10x magnification.
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Can I adjust the eye relief power in binoculars?
The simple answer is yes.
In good-quality binoculars, you should be able to adjust the eye cups. Some brands may even offer 3-4 eye cup positions. You may even be able to remove padded cups to get in closer to the lens.
A fully retracted eye cup is one that is pushed all the way in.
This is the one you’ll want to use if you wear glasses as it will help to shorten the eye relief and get your glasses close to the ocular lens.
This is a great setting to use if you have deep-set eyes as it can be more comfortable on your eyes.
Just be careful with the lens at this position as it’s more exposed to dirt and lens damage.
A fully extended eye cup will be pulled out as far as it will go.
This setting is only really suitable if you don’t wear glasses or have deep-set eyes.
Pulling the eye cup all the way out will help to cut down on peripheral light to help you focus better.
Depending on how far the eye cup extends this may slightly reduce your field of view.
Also, be aware that fully extending the lens may result in your lens fogging. This is due to warm air being trapped in the eye relief area.
A middle extension is the setting between fully retracted and fully extended.
This is an ideal middle ground if you don’t wear glasses. You may even find this setting suitable if you have thin glasses.
That way you get the benefit of reduced peripheral light and reducing the risk of lens damage.
Eye relief Explained
6 Best Binoculars For Eye Relief
1. Zeiss Victory SF
This 8×32 version provides 19mm eye relief.
2. Vanguard Endeavor ED
The 8x42mm version provides 19mm eye relief.
3. Nikon Monarch 5
The 8×42 version provides 19.5mm eye relief.
4. Nikon PROSTAFF 3S
The 8×42 version provides 20.2mm eye relief.
5. Vortex Viper HD
The 8×42 Binoculars provide 20mm eye relief.
6. Pentax DCF ED
The 8×43 version provides 22mm eye relief.
Eye Relief is a feature you need to know about when buying binoculars.
Especially if you wear glasses or have deep-set eyes.
Finding binoculars with the right length of eye relief will make the difference between you getting a good view, or missing out on some of the picture.
By using the guidance in this post you should be able to find a good pair of binoculars that have enough eye relief to get a great view of the birds.
If you’re a glasses wearer let me know which binocular you recommend or one to avoid in the comment below.