Binoculars Eye Relief-What You Need to Know
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Binoculars eye relief is an important factor to consider when choosing your binoculars especially if you are an eyeglass wearer or shooter. Choose the right binocular with the wrong eye relief and it will mess up your comfort of viewing through them.
Why eye relief is particularly important to shooters is that is considered a safety feature. If the eye relief for the scope sight is too short, which then leaves your eyes too close to the sight, when you shoot, the firearm’s recoil can force the optical eyepiece to hit and cut into the skin around the shooter’s eye. Due to the obvious and long-lasting nature of this mistake, it is often called “scope bite” or the “idiot cut”
What is Eye Relief in Binoculars?
Eye relief in binoculars is simply the ideal distance your eyes should be from the binocular eyepiece last surface for you to obtain a full viewing angle. The eyepiece lens is the lens which is closest to your eye.
Viewing an image within the correct eye relief is important because if your eye is further or too close to the eyepiece than required, you will lose the outer edge of the picture.
That’s why it is important for glass wearers to get the right binoculars with long enough eye relief to accommodate their eyeglasses. otherwise, you will have a hard time seeing the full picture.
This can put a strain in your eyes as a result of trying hard to see through your device. Which is why some people complain of eye fatigue after using binoculars for a just short time.
The eyepieces often have eyecups attached to them. These can either be retracted or extended to get the right eye relief for yourself.
How to get the Right Eye Relief- Adjustable Eye Relief
Binoculars are some of the optical instruments that come with adjustable eye relief. When a binocular has an eye relief of 16mm, eyeglass wearers are able to use them with comfort but you if with that same binocular, the eyecup was twisted out, the same glass wearer will have to strain their eyes to be able to see the entire field of view.
This is because when you extended the eyecups, you lost some of the distance and you are only left with just left with less than the desired eye relief.
To obtain the ideal eye relief for yourself whether you are glass wearer or not, you need to play around with the eyecups to reach that position whereby you are comfortable and can get the entire field of view.
Tip: Glass wearers should keep the eyecups retracted as much as possible while non-glass wearers can keep their eyecups extended. Read more on Adjusting binoculars focus.
Most eyecups on binoculars have multi-position adjustments which allow more flexibility of viewing, give you comfort and eye safety for both glass and non-glass wearers.
Magnification, Field of View and Eye Relief- How They are Related
Binocular Magnification is how many times closer the object you are looking at will appear to your eyes when you look through the binos. You may like to read this article on understanding magnification better. This number alongside the objective lens diameter are often printed and shown boldly on the chassis or the focus wheel of the binoculars.
An example is 8×32. The magnification is the first number (8×). It means that when you view an object through this binocular, the object will appear eight times closer to your than your naked eye would see.
On the other hand, the field of view is often measured in linear or angular form. It is the open observable area a person can see through his or her eyes or via the optical device. An example is 393.7′ @ 1000 yd.
So how do the magnification and the field of view relate to the eye relief?
Well, the more you increase magnification, the more you will be compromising the field of view by reducing it. This also, in turn, reduces the eye relief that you will have on your optical device.Іt’ѕ thе wау thаt орtісаl рhуѕісѕ wоrkѕ. Yоu іnсrеаѕе роwеr, уоu rеduсе fіеld оf vіеw аnd еуе rеlіеf. Іt’ѕ а trаdе-оff. Ніgh роwеr еquаlѕ lеѕѕ еуе rеlіеf. Lоw роwеr еquаlѕ mоrе еуе rеlіеf.
The best way to go round that is always look for the maximum field of view and the min field of view for your device if you have variable zoom or magnification. If you have fixed magnification binoculars, just adjust your eyecups for best full viewing.
Long Eye Relief
Long eye relief is often desired in optics. Long eye relief is often considered anything around 20-24 mm for binoculars. This allows for more forgiving distances for those who wear glasses and its comfortable to use binos with such generous eye relief. Because you won’t have to place your eyes directly on the eyepieces.
Short Eye Relief
Eye relief isn’t a problem experienced by all. This is an issue that mostly affects glass wearers and as mentioned earlier on shooters. Short eye relief is typically anything less than 13 mm. For those who don’t wear glasses, this might not be a problem. But you might feel like you are straining your eyes to see the entire field of view.
The reason why getting the correct eye relief is important is that when you place your eyes outside the recommended eye relief distance, whether too close or too far, you will run into viewing problems.
Minimum Eye Relief for Glasses
Typically the eye relief distance recommended for glass wearers is 16 mm or more for comfortable viewing. Otherwise, they might experience viewing difficulties with shorter eye relief distances.
This is because the glasses can get in the way of viewing and thereby reducing the eye relief distance. Most binoculars have eye relief around the 15 to 17 range.
Optical Instruments that have Eye Relief
Below are some of the optical instruments that have eye relief on them:
- Spotting Scopes
- Handgun Scopes
- Scout Scopes
In conclusion, binoculars eye relief often is not a major problem to non-glass wearers and even these days manufacturers are adding the eyecups and diopters to binoculars for those who are short-sighted or far-sighted to be able to adjust their binos and get the ideal field of view without their glasses.
However, if you are a person who can not look through your binoculars with glasses. It is important when you are choosing binocular, you seriously consider the eye relief.
Josephine is Content Manager @ Binocularsinght.com, an Electrical Engineering Grad who loves optics. She is an Outdoor Enthusiast and a Writer who likes escaping into the mountains for hiking adventures and enjoys other outdoor activities as well.