Last Updated: March 2, 2023
Binoculars are an essential tool for many outdoor activities, including hunting, bird watching, and stargazing. However, few people pay attention to eye relief when selecting binoculars. Eye relief is the distance between the eyepiece and your eye that allows for a comfortable viewing experience.
It's an important factor to consider when choosing binoculars because insufficient eye relief can cause discomfort, eye strain, or even injury. In this article, we'll discuss what eye relief is, why it matters, how to measure it, and what constitutes good eye relief.
Click on the following link to learn about all the essential factors and recommendations to consider when choosing your binoculars. Moreover, if you lack familiarity with the functioning of binoculars and require knowledge and skills to optimize their performance, I recommend you read my all-inclusive guide on using binoculars correctly.
What Is Eye Relief?
Eye relief is the distance between the eyepiece lens and your eye that allows for a clear and comfortable viewing experience. It's an important factor to consider when selecting binoculars, as it determines how far away from the eyepiece your eye can be and still see the entire field of view.
Eye relief is particularly important for people who wear eyeglasses or sunglasses, as they need more distance between their eye and the eyepiece to see the entire field of view. If the eye relief is insufficient, they may need to remove their glasses to see clearly, which can be inconvenient or uncomfortable.
The physics behind eye relief is based on the concept of the exit pupil. The exit pupil is the diameter of the light beam that exits the eyepiece lens and enters your eye. The diameter of the exit pupil is determined by the diameter of the objective lens (the front lens) divided by the magnification of the binoculars. For example, a pair of 10x42 binoculars will have an exit pupil of 4.2mm (42/10=4.2).
The position of the eyepiece lens relative to the exit pupil determines eye relief. The eyepiece lens must be positioned so that the exit pupil is fully visible in your field of view, and your eye must be positioned at the correct distance to see the entire field of view.
If the eyepiece lens is too close to your eye, the exit pupil will be partially obscured, resulting in a smaller field of view. If the eyepiece lens is too far from your eye, the exit pupil will appear as a smaller circle, and the image may be difficult to see.
Why Is Eye Relief Important?
Eye relief is important for binoculars because it affects the viewing experience. If the eye relief is too short, the eyepiece will be too close to your eye, causing discomfort, eye strain, and even injury. You may also have trouble seeing the entire field of view, which can be frustrating and may cause you to miss important details.
In addition, people who wear eyeglasses or sunglasses may have difficulty seeing the entire field of view if the eye relief is insufficient. They may need to remove their glasses to see clearly, which can be inconvenient or uncomfortable.
On the other hand, if the eye relief is too long, you may have difficulty seeing the entire field of view because your eye will be too far from the eyepiece. This can also cause eye strain and discomfort, as your eye will need to work harder to see the image.
Examples of how insufficient eye relief can cause discomfort or injury include eye strain, headaches, and even black eyes. When using binoculars with short eye relief, your eye may be too close to the eyepiece, and the edges of the eyepiece may press against your eye socket.
This can cause discomfort or pain and may result in a black eye if the binoculars are jostled or moved suddenly. To avoid these issues, it's important to choose binoculars with sufficient eye relief for your needs.
How To Measure Eye Relief?
Measuring eye relief requires a few simple tools, including a ruler or measuring tape and a tripod or other stable surface to support the binoculars.
Here are the steps for measuring eye relief:
- Set up the binoculars on a stable surface, such as a tripod or table.
- Adjust the eyepiece to the correct distance for your eyes.
- Place the end of the ruler or measuring tape at the center of the eyepiece lens.
- Look through the eyepiece and move the ruler or measuring tape away from the eyepiece until the entire field of view is visible.
- Take note of the distance between the eyepiece and the point where the ruler or measuring tape is visible in the field of view. This is eye relief.
To ensure accurate measurements, it's important to keep the ruler or measuring tape straight and perpendicular to the eyepiece lens. It's also important to position your eye at the correct distance from the eyepiece to ensure that the entire field of view is visible.
If you wear eyeglasses or sunglasses, be sure to keep them on while measuring eye relief to ensure that the measurements are accurate for your needs.
What Is A Good Eye Relief?
Good eye relief in binoculars is typically considered to be around 15-20mm, although some people may need more or less depending on their individual needs. Eye relief of less than 10mm is generally considered insufficient for most people, while eye relief of 20mm or more is considered very good.
Different types of binoculars may have different eye relief, depending on their design and intended use.
For example, compact binoculars may have shorter eye relief due to their smaller size, while long-range binoculars may have longer eye relief to accommodate people who wear eyeglasses or need more distance between their eye and the eyepiece.
Examples of binoculars with excellent eye relief include the Vortex Optics Viper HD 10x42, which has an eye relief of 17mm, and the Leica Ultravid HD-Plus 10x42, which has an eye relief of 17mm. These binoculars are designed for bird watching and other outdoor activities and are known for their high-quality optics and comfortable viewing experience.
Other binoculars with good eye relief include the Nikon Monarch 5 8x42, which has an eye relief of 19.5mm, and the Celestron TrailSeeker ED 10x42, which has an eye relief of 17.5mm. These binoculars are also designed for outdoor use and are popular among birdwatchers and nature enthusiasts.
When selecting binoculars, it's important to choose a pair with sufficient eye relief for your needs to ensure a comfortable and enjoyable viewing experience.
In conclusion, eye relief is an important factor to consider when choosing binoculars. Eye relief is the distance between the eyepiece lens and your eye when you view through the binoculars.
Good eye relief is typically around 15-20mm, although this can vary depending on your individual needs. Insufficient eye relief can cause discomfort, eye strain, and even injury, while excessive eye relief can make it difficult to see the entire field of view.
To measure eye relief, you can use a ruler or measuring tape and a stable surface to support the binoculars. When selecting binoculars, look for a pair with sufficient eye relief for your needs, and consider the type of binoculars and their intended use when comparing eye relief measurements.
By taking eye relief into account when selecting binoculars, you can ensure a comfortable and enjoyable viewing experience, whether you're birdwatching, enjoying a sporting event, or simply exploring the great outdoors.
At the end, I would recommend all the passionate bird watchers and ornithologists to read my article regarding the Best Binoculars For Birding to make an informed decision while purchasing one.