Rifle Scope And Spotter Terminology Guide

This page contains information and definitions of terms commonly used for rifle scopes and spotters. Having at least a basic understanding of the meaning of these terms will help you greatly in your search and use of scopes. The more you know about a scope and the better you understand the features the better your final decision will be.


Lenses in every type of optic, whether it is your scope of photo camera, have special types of coatings that help with the reduction of light loss and especially glare. Different types of coatings result in different results when it comes image sharpness, brightness and contrast, and the better results you want to achieve the higher the price tag will be.

Eye Relief

This is defined as the distance between the rear lens (closest to the eye) to a point where you will see the full field of view. This is something important to consider for numerous reasons. If you wear glasses you need to account for a different distance as the lens of your glasses will be closer to the scope than your eye. The recoil of a rifle will essentially push the scope closer to your eye and you need to avoid your eye and face making contact with the scope.

Light Transmission

This is closely related to the coatings of the lens and it is a measurable feature of a scope. Most manufacturers will highlight light transmission for each scope as a percentage of available light. In very bright conditions this may not be a huge problem, but if you are shooting in low light conditions like at dusk or dawn, then you will need something with a very high percentage of light transmission.


This is also a very important factor of each scope you will see. It essentially tells you how far you can zoom in an object, just like on a camera. As an example a 3 to 12x scope will allow you to zoom in from 3 times to 12 times closer to the object than the bare human eye would be able to see.


The scope’s mount is very important and you should always check whether you have the right mount. This is a very important part to get right, as it will hugely impact the usability of the scope. If the scope is not mounted correctly it can result in unwanted adjustment and movement, which will essentially render it completely useless. Most scopes come with their own mounts and are often made to fit standard rifle mounts as well.


Parallax is possibly one of the most widely misunderstood terms when it comes to scopes. In essence it is the appearance of the reticle moving in relation to your target, even though your rifle is completely stationary. You will most likely notice this when you move your head a little while looking through the optics.

Many scopes these days will come with a side adjustment for focus as well as parallax, which will help your scope become parallax free, i.e. in a state where moving your head does not result in the reticle moving. While a picture paints a thousand words, we found that this video makes an even better job at explaining this phenomenon.


The reticle is the crosshairs you see when looking through the scope. Designs of these vary widely mainly dependent on use, where tactical scopes will differ to long range target shooting scopes for example. Ultimately it is a mixture of preference and usage that will dictate what you choose.


If you fire a rifle in dark conditions you will actually see the trajectory it takes and dependent on your angle of view you will notice two things. Looking from the side you will notice that the bullet will travel in arc. This is essentially the effect of gravity on the bullet and the arc will depend on the velocity and weight of the projectile. Looking from behind you may notice a bullet moving from side to side if or when wind is present. Both these things can be compensated for using the turret adjustment knobs.


The scope turret is made up of two knobs which will be located at the center of the scope. The adjustments made with the turret allow the user to compensate of wind and elevation when taking aim. Each click of the knob will make a predefined adjustment and the smaller the click adjustment the more fine-tuned the scope will be.


Every scope will have a defined zero, which is the distance at which it is sighted at. For example, a scope with a 100 yard zero means that the point of impact for caliber and bullet is 100 yards. From this you will make adjustments for the distance of the object with the turret knobs.