When kitting out a new rifle, it’s important to recognize that your rifle scope is just as important as the rifle itself. Your optic can either make or break your performance, leading to either an awesome shooting experience or a less-than-stellar one. The choice for optics is near limitless, and like most other accessories, there’s a lot to consider whenever you’re choosing one.
One of the most crucial factors that determines a scope’s effectiveness is eye relief. Eye relief is the distance your eye needs to be from the ocular lens to see the entirety of your scope’s FOV without any obstruction or scope shadow. No matter what your build is tailored for, proper eye relief ensures a clear and unobstructed sight picture through the scope.
By understanding eye relief, you can ensure that you’ll see the best sight picture possible, regardless of what optic you use.
What is Eye Relief on a Scope?
Like we said above, eye relief refers to the distance between the ocular lens of your scope and your eye where you can see the full field of view. This distance varies depending on the optic but understanding and achieving proper eye relief is essential for optimal performance.
Proper eye relief plays a critical role in how rifle scopes work, allowing you to focus on your target and see all your optic’s reticle elements clearly. Without the correct eye relief, your sight picture will become constricted by scope shadow. Scope shadow is an optical effect in which you’ll see a dark ring around the image, occurring when you’re too close or far from the optic. With proper eye relief, however, this won’t be an issue.
Does Eye Relief Change with Magnification?
In variable magnification scopes, your magnification setting can affect your scope’s eye relief.
As magnification increases, eye relief decreases—but not by much. Generally, most rifle scopes usually have an eye relief distance of around 3.5-4 inches at their minimum magnification. At max magnification, the eye relief distance might change to somewhere around 2.5-3 inches. Such a minor change only requires you to adjust your head position slightly.
Of course, the easiest way to accommodate the change is having a good mounting position. When mounting a scope, you can move it either further forward or back, depending on your preference, allowing you to find a position that works best for you.
Does Eye Relief Affect Accuracy?
Mechanically, no. But practically speaking, it absolutely does. As we’ve mentioned, proper eye relief allows you to fully utilize your scope to the best of its ability.
In applications that require precise marksmanship, proper eye relief is non-negotiable. The same thing applies for hunting, competitive shooting, and even recreational outings. At the end of the day, proper eye relief is crucial for achieving consistent shot placement. Without it, your chances of maintaining accuracy are slim at best.
When setting up your scope on your rifle, you’ll also want to position it in the mount that best corresponds with the position you’ll be shooting in. Take the prone position for instance. When shooting prone, your scope will need to be set farther forward for optimal eye relief compared to standing or bench shooting. We recommend trying out different scope positions when mounting one to help you find the best positioning possible.
If your build is geared more towards precision shooting, there are a lot of optics that are great for the job. Our long-range scope buyers guide goes in-depth on the different makes and models available that are designed for performance and longevity.
Difference Between Eye Relief and Exit Pupil
While eye relief is crucial for comfortable and accurate shooting, the scope’s exit pupil is another critical factor that affects its overall usability.
Exit pupil refers to the width of the image that’s projected by the ocular lens of your scope. Mathematically, a scope’s exit pupil can be calculated by dividing the diameter of the objective lens by the magnification level it’s set to. However, not all scopes are the same. Although it’s mathematically correct, this equation won’t give you the exact exit pupil diameter, but rather the maximum diameter it could be based on your scope’s settings.
The actual exit pupil size of modern rifle scopes is usually slightly smaller than the maximum diameter, which is done to enhance their clarity and overall sight picture. Since no scope is truly identical to another, the actual exit pupil diameter can vary from scope-to-scope, making it exceedingly difficult to accurately calculate. Despite being difficult to calculate, good quality scope options will offer a great exit pupil and sight picture, so there isn’t too much to worry about.
The exit pupil size also determines how much light reaches your eye. All things equal, the smaller the exit pupil is, the dimmer your sight picture will be, and you’ll have a less forgiving eye box that will essentially lock you into only one position when using your optic. Larger exit pupils provide you with a brighter overall sight picture and a bigger eye box window, giving you more space to comfortably sit behind the optic without seeing any scope shadow.
Keep in mind that scope shadow can be useful, at times, particularly when using a scope with fixed parallax while shooting at long distances. In this case, scope shadow can be an aid for achieving proper head placement and sight alignment, using it in the same way you would use a peep sight. So long as you have an even scope shadow around your sight picture, you’ll be aligned with the scope’s optical center, reducing the chances of introducing parallax shift.
Understanding Eye Box
So, we’ve mentioned it a couple times thus far, but what exactly is your scope’s eye box? Many enthusiasts often incorrectly believe that an optic’s eye relief is synonymous with the eye box, but that’s not really the case. As we mentioned previously, your scope’s exit pupil arguably plays a much bigger role in your overall ability to see through your optic.
Essentially, the eye box is the usable space behind your optic in which you can look through it and see the target picture with no scope shadow or occlusion. Despite being called the eye ‘box’, it’s functionally more cylindrical than box-like. Either way, to effectively see your sight picture, your head position and eye need to be within the eye box of your scope.
Combined, your eye relief and exit pupil determine how big your eye box is. The eye relief is the length, while the exit pupil is the diameter. The larger the eye box is, the more “forgiving” an optic is. This usually equates to a faster optic, allowing you to get behind the glass, identify a target, aim, and engage faster Just remember, as your magnification increases, your eye relief and exit pupil diameter will decrease, this will make it a little slower to properly align yourself behind the scope for a good sight picture, which is why high magnification settings can feel more constrictive to use
Eye Relief on Different Optics
Long Eye Relief Scopes
We touched on this before, but on average, a rifle scope is going to have an eye relief of around 4 inches, however, eye relief distance varies depending on the optic. In most cases, the difference is subtle, having around a 1- to 2-inch difference, but in extreme circumstances though, your rifle’s design might require a rifle scope is a long eye relief, like on scout optics. Scout scopes are designed for rifles that follow Col. Jeff Coopers “Scout Rifle” concept with further-than-average mounting locations, like some M14/M1A models, Steyr Scout Rifles, or the Ruger Gunsite Scout, for example.
On rifles like these, optics sit towards the middle of the rifle, over the barrel, instead of further back on the action. Because of how far these optics sit on the rifle, they need to have incredibly long eye reliefs like 8 inches, with some optics having as long a 12- to 14-inch eye relief distance.
Generally, unless you’re using a scout rifle setup, you won’t need to use a scout scope. Most modern rifles allow you to easily mount optics where you’ll be able to get ideal head placement for standard optics.
Prism Scopes
Prism scopes have a lot of advantages for rifles like AR-15s. They’re much lighter than traditional rifle scopes and are comparable to reflex sights in terms of size. Still, they’re another type of magnified optic that can have varying eye reliefs.
Optics like our SLx® and GLx® 1x MicroPrism™ Scopes have a usable eye relief range of 2 to 6 inches. However, the most optimal distance is 3.6 inches. As you step in magnification, the optimal eye relief of the optic starts to become more constricted. For instance, on our SLx 3x and 5x MicroPrism scopes, the optimal eye relief is around 2.7 inches.
Since these prism scopes don’t have variable magnification, the eye relief isn’t subject to change, unless you use a magnifier that is. However, magnifiers can be used effectively on our SLx and GLx 1x MicroPrism Scopes. In this case, your usable eye relief will shrink to around 2.4 inches.
If you’re more interested in using a prism scope, our guide, “What is a Prism Scope?” will fill you in on what to consider before pulling the trigger on one.
Reflex Sights
Reflex sights are by far some of the most popular optics around, but how does their eye relief compare to the others mentioned thus far?
Reflex sights, like most modern red dot sights, have no magnification and essentially 1-to-1 fields of view. For red dot sights, light is projected from a diode which is collimated on to the lens of the optic to form the reticle. Holographic sights are a bit different. Instead of reflecting light off one surface, the light is reflected off multiple surfaces, forming the holographic image within the optic.
Either way, reflex sights have effectively infinite eye relief. That is, if you’re looking through the optic at the target, you should see the reticle.
Conclusion
An optic’s eye relief, exit pupil, and eye box all play an immense role in defining the utility of your scope. As a result, having the right combination of each is vital in becoming more proficient when using your optics.
Remember, every optic differs slightly from another, with some rifle and optic combos being more effective. It’s important to take time to really examine each of your prospective optic choices before choosing one. If possible, we recommend trying out different combinations to see if there’s one that you prefer more.
At the end of the day, whether you opt for one of our scopes or another type all together, if the optic you go with provides with you the optimal performance you need for your purpose, you’ve chosen wisely.
If you’re still on the fence about what rifle scope is the best one for you, check out our guide on what the numbers on scopes mean. It goes over more of the technical details about rifle scopes, giving you more insight into what to look for when searching for yours.
