When you're talking optics, there's a scope application for just about everyone. Many people are loyal to certain brand names regardless of price while others are just looking for a great deal. No matter what your reasons, you'll have to choose based on your shooting criteria. In other words, you'll want to match the proper scope to whatever type of shooting you'll be doing.
In this article, I'm going to focus on the subject of extended eye relief and tell you why it is the most important feature when choosing a handgun scope. A little knowledge can go a long way before making your scope selection.
But before I go into how it works, I want to give you a brief, "general" description of what Extended Eye Relief is. Some readers might be new to the subject, so I'll want to get them up to speed.
Essentially, eye relief is the distance between your eye and the rear lens (ocular lens) of the scope when the full field of view is visible.
Now that might seem like a very simplistic definition of what EER is, but how do you actually determine proper extended eye relief with a full field of view?
Try this. The next time you look through a scope, move your head around or the scope varying distances from your eye. You'll begin to notice a black ring or shadow in your site picture. When the black ring or shadow is completely eliminated from your picture, your target should fill the entire inside diameter of the eye piece and be completely centered within the scope. Once you see that, you'll know you have a full field of view and you'll be able to measure the distance of eye relief.
This is critically important when choosing a handgun scope because you'll probably be holding the scope anywhere between 5 to 30 inches away from your eye. If you don't have the proper full field of view at these distances, you'll have to adjust your shooting stance in order to accommodate the scope, something you'll want to avoid because your shooting accuracy will more than likely suffer.
Keep in mind that your goal is to make the scope work for you, not the other way around.
Something you should also know is that Extended Eye Relief changes with magnification in variable power scopes. Generally speaking, the higher the magnification the less eye relief you have. This is important for those hunters or competition shooters whose target sits at a significant distance.
When higher magnification is used, the field of view narrows sometimes making it a little more difficult to acquire the target, especially if the target is moving. The trade off is that even though there is less visual information for you to process, the target is magnified by the number of times you dialed in on the scope, making it easier to see your target once it's in your field of view.
If, however, you're going to be hunting or shooting in areas where your shots will be close and you're not using a rest, then you'll need little magnification and a large field of view. A larger field of view will always allow for quicker target location, especially one that's difficult to see with the unaided eye.
Just make sure that you have the proper field of view as discussed earlier.
Some of you may be wondering what the magnification numbers from the spec. sheet actually mean.
Let me explain. Let's say you have a scope that is 2x20mm. The first number is the apparent magnification power where 2 means your target looks twice as large through the scope as it does over iron sights. The last number, 20, is the diameter of the front lens (also called the objective lens) measured in millimeters. In general, the larger the objective lens, the more light gathering capabilities it carries and can therefore be used in lower light conditions.
Because in the above example there is no other number associated with the number 2, this tells you that this is a fixed power scope. If it were written 2-8x28mm, then this would be a variable power scope with 2 being the lowest magnification and 8 being the highest magnification. Again, the 28 represents the size of the objective lens in millimeters.
Why are these numbers so important? Because not only will it tell you what the magnification of the scope is but also the diameter of the exit pupil once you know the formula.
Before I get into how to calculate the exit pupil, I'll bet you're wondering what an exit pupil is. This may get a little technical so please bear with me.
Here's how it works. A scope gathers light over the face of its front or objective lens and concentrates it out into the eyepiece in an area called the exit pupil.
The exit pupil of your scope should match the pupil size of your eye as closely as possible (or just a little larger) to get maximum low light performance and prevent scope blackout. You calculate the exit pupil diameter by taking the objective lens diameter (front lens closest to your target) and dividing it by the scope power.
For example, a scope with a 20mm objective lens and a power magnification of 2 will have a 10mm exit pupil. 7 to 8mm is about the maximum size that the human pupil will dilate in low light, so this scope will work well under low light conditions. A smaller exit pupil would not deliver as much light to the eye as the eye is willing to accept, however, a large exit pupil means that the eye does not have to be as precisely centered behind the scope to receive a full image.
For adjustable power scopes, 3-9x40mm for example, you get the exit pupil based on the power setting of the scope. For example: 40 divided by 3 = 13.33mm exit pupil and 40 divided by 9 = 4.44mm exit pupil. As you can see, the higher the magnification, the smaller the exit pupil, hence the lower the light gathering capabilities at higher magnifications.
When talking about light gathering capabilities, you'll want your exit pupil to be the same diameter or just a little larger than the conditions you're using the scope in. For instance, if your eye's pupil is dilated to 5mm, and the exit pupil of the scope is 7mm, then you have 2mm of leeway before your eye position behind the scope becomes critical.
If the exit pupil of the scope is smaller than the diameter of your eye's pupil, you'll start to encounter problems seeing the full image of your target.
Just as a frame of reference, the human pupil is normally dilated to about 5mm in standard light, 2-3mm in bright light, and 7-8mm in low light conditions.
Whew … I know my description was a little technical, but knowing what the exit pupil is and how it works will help you determine how to best utilize your scope.
You might also be wondering how the exit pupil calculation, light gathering characteristics, and scope magnification tie in with extended eye relief? Just remember, for EER handgun scope applications you'll be holding your scope anywhere from 5-30 inches away from your eye. This can be a significant distance if your scope does illuminate your target well enough and the position of your eye is not aligned with the exit pupil. These have a significant affect on EER, making it difficult to get off an accurate shot if not taken into account.
And … speaking of accurate shots, there are a few handgun scopes I recommend to give you the best chance of accomplishing those shots.
I think some of the best handgun scopes for Extended Eye Relief and light gathering capabilities are the Nikon EER Monarch series, the Leupold FX and VX series, and the Burris LER series. All three companies offer exceptional choices in optics as well as full lifetime guarantees. They're rugged and durable and 100% waterproof. They have unmatched lens coating systems which excel in brightness, clarity, and contrast.
Few companies are able to stack up, however, you'll have to make the best choice for your shooting application and go with the scope and company you feel most comfortable with.
They're not the cheapest scopes, but they're best overall value and definitely worth the investment.
Hopefully I've clarified questions you might have had about scope definitions and how to calculate critical components of a scope. Now, with this information, you'll be armed with the knowledge you need to make a wise EER scope selection.
Oh … one more thing. Usually, the amount of eye relief and magnification is listed in the specifications by most manufacturers, so you should be able to get a good feel for what you need after applying the knowledge you've gained from this article.
Copyright 2005 © John Voight
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