Welcome to Optics Trade debates. In each episode, we talk about a different topic and try to answer the most common questions we receive about it. Today, we are going to talk about eye relief.
Eye relief is measured in millimeters. The distance is measured from the eyepiece lens to the focus. The longer the eye relief is, the better it is.
Binoculars with a long eye relief are generally more comfortable to use with glasses. With scopes, the eye relief is important because of recoil. If the eye relief is too short, the scope can hit the user when the gun recoils. Old rifle scopes had a really short eye relief and their users could get hit in the head if they weren’t holding the rifle firmly.
On binoculars, 16 mm is considered a good eye relief and everything above 18 mm is even better. There are even binoculars that have a 24 mm eye relief and are very comfortable to use.
The eye relief on riflescopes starts at 70 mm but 90 mm is most commonly used. Premium manufacturers make scopes with an eye relief of 100 mm and even up to 120 mm for African magnum calibers.
Scout and handgun scopes have a 300-400 mm eye relief.
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Explanation of the term on our website:
The only way of obtaining the whole field of view is to have the right distance between the eye and eyepiece – referred to as the eye relief. The eye relief is not necessarily a decisive factor in choosing the right optical product, however, it is a useful information if you wear glasses. The eye relief then should be at least 16 mm for comfortable viewing and getting a complete image. Binoculars with too short eye relief give people with glasses a tunnel vision and only show the middle part of an image. With riflescopes, the optimal distance is 90 mm or even more for safety reasons (recoil).
Without glasses, the distance when using binoculars should be minimum of 15 mm, although everyone has a preferred placement as long as they’re obtaining a complete field of view with no blurry edges.
Most binoculars have movable eyecups, where you can adapt them to fit different face structures (if your eyes are further away from you nose etc.) and therefore maintain a steadier grip. If you wear glasses, the eyecups should be closed down so you can lean them onto your glasses.