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Understanding Optics Terminology

If you want to get the most from your sights and scopes, you need to understand optics terminology. While knowing the lingo may give you some range cred when talking with the guys, there’s a much more important reason to understand what all these strange words and designations mean. It helps you make a more informed decision when buying precision optics for your firearms and helps you use those optics more efficiently to shoot better. Whether you’re using a traditional scope left to you by your pappy or your gun is sporting one of our innovative sight designs, understanding the proper use of your firearm–including the installed optics-is a must for safe operation.

Types of Optics

The first thing you need to understand about firearms optics terminology is that not all optics function the same. While guns and their immediate precursors have been around for almost 1000 years, they’ve changed a lot. The way people aim them has had to change to keep up, and today’s precision optics can be far different than those used by previous generations. Most optics now fall into one of three categories: traditional scopes, prism scopes, and reflex sights. Whichever you choose, there are some terms that are universal.

  • Field of View – The observable area you can see within the boundary of your optics. 
  • Magnification – Some precision optics are designed to enlarge the field of view over what it appears to be with the naked eye. This magnified view makes it easier for precision aiming, but in the process, you lose sight of the area directly outside the field of view that’s blocked by the body of your optics. Magnification can be either fixed or adjustable within a range.
  • Ballistics -Bullets don’t travel in a straight line, rather they begin to drop as soon as they leave the barrel, pulled downward by the Earth’s gravity. They can also be affected by wind and other atmospheric conditions. Ballistics is the science of how projectiles fly through the air. You will often hear the term ballistic arc describing a bullet’s trajectory, or path, from the barrel of a gun aimed slightly upward as it rises and falls on the way to the target.
  • Windage Adjustments – Some optics will have a knob, turret, or screw that allows you to adjust your aiming point horizontally to compensate for the presence of wind that affects your bullet’s trajectory.
  • Elevation – Some optics have a knob, turret, or screw that allows you to adjust the elevation of your weapon’s barrel in relation to your aiming point. This lets you sight your weapon for a reliable ballistic arc that causes the bullet to meet the target at your aiming point.
  • Mount – The way your optics connect to your firearm. This piece of optics terminology is often accompanied by a description of the type of mount involved, for example, Weaver, scope rings, or RMR. Your weapon will likely be configured to accept certain mounting options, or aftermarket gun parts may be available to add that functionality.
  • Eye-Relief – The distance from the eyepiece fo your optics where the shooter’s eye should be for accuracy. Some optics have a set distance that is recommended, while others may offer unlimited eye relief, meaning they are designed to provide a clear sight picture from any distance.
  • Cowitness – This describes precision optics that are designed to use your weapon’s iron sights to complete the sight picture. Absolute cowitness lines up your optics with your iron sights perfectly, while lower ⅓ cowitness places your iron sights in the lower part of your field of view.
  • MOA/MIL – Minutes of Accuracy and MILliradians are both optics terminologies that refer to measures of angle that describe how much an adjustment will move your aim point in relation to the weapon’s barrel. An MOA is equivalent to about one inch at 100 yards, while a MIL is about three inches. It’s important to note however, that precision optics usually adjust in either ¼ MOA increments or 1/10 MIL increments, giving a very close practical adjustment of around ¼-inch with either standard. MOA is sometimes also used to refer to the angular deviation in a group of shots fired at the same aim point.
  • Reticle – The printed or projected aiming aid of your optics within the field of view. This can be a traditional cross-hairs style or any number of configurations designed to help you have an accurate aiming point for better shooting.

Traditional Scopes

Traditional scopes use a series of lenses for precision shooting. These will usually offer magnification and are easily recognized by the long tube with one or two flared ends sitting atop the weapon. Traditional scopes remain popular for those who require longer-range accuracy from their weapons.

  • Objective Lens – The lens closes to the target. This lens is usually referred to by a number giving you its size in millimeters, a magnification multiplier or multiplication range, and a decimal that signifies the numerical aperture for light gathering. Larger objective lenses take in more light to create brighter, more detailed images fo the shooter.
  • Ocular Lens – The lens closest to the shooter’s eye inside the eyepiece. The light emitted is projected onto the shooter’s eye providing the sight picture needed for improved accuracy.
  • Other Lenses –  The inside of your scope can have a number of other lenses depending on its design. These can focus colors, correct the image to avoid aberrations, and align the reticle with your sight picture properly.
  • Turrets – The windage and elevation adjustment knobs on a scope.
  • Gas Charged – These scopes are filled with an inert gas that eliminates moisture to prevent atmospheric conditions from literally clouding your sight picture.
  • Reticle Types – There are many different fixed scope reticles that allow you to compensate for windage, distance, and bullet drop without making adjustments to the scope itself. 

Reflex Sights

Sometimes referred to as holographic sights, these sights are built for fast target acquisition in dynamic situations, such as range drills or for tactical use. These feature a light projected onto a lens to provide an easily identifiable aiming point for close-range shooting, even in low-light situations.

  • Emitter – The small LED laser that projects an image onto your sight’s lens, creating a reticle that can only be seen from a specific angle. 
  • Closed Reflex Sights – Closed reflex sights consist of a tube capped on both ends with a lens. This helps protect the emitter but at the expense of a greater field of view blocked by the larger sight.
  • Open Reflex Sights – Sometimes called red or green-dot sights, open reflex sights project the light directly onto the single lens of the system, which sits within a frame, offering an almost unlimited field of view.

Prism Scopes

Prism scopes occupy the middle ground between scopes and reflex sights, often appearing as shorter versions of traditional scopes, albeit with the technological exterior associated with reflex sights. They are slower to acquire targets than their close-range counterparts, but offer limited magnification for better accuracy as distances increase, making them popular for rifles and carbines.

  • Prism – Prisms are shaped to refract or reflect light, and prism scopes use prisms between the objective and ocular lenses to focus and align your target in the field of view. 
  • Diopter – Like traditional scopes, the image that you see can be adjusted to accommodate personal visual acuity, compensating for astigmatism for better accuracy.
  • Dual Reticle – Prism scopes feature both an etched reticle like that found in traditional scopes and an emitted reticle to offer the best of both worlds to the shooter. 

Getting More From Your Optics

While this gives you a place to start with optics terminology so you can better understand the sights and scopes available for your weapon, using them properly requires patience, practice, and diligence. We’re happy to help. Please reach out with our contact form if you have any questions, and keep an eye on our blog for the best ways to dial in your precision optics for better shooting. Upgrade your firearm with some of the most innovative and reliable optics available. Order your performance optics from Gideon Optics today.

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