If there is one term that is hugely misunderstood among shooters and hunters, then it’s parallax. For most shooters, parallax is merely bringing the reticle into focus!
But that’s far from the truth.
So what does parallax mean? And how do you go about correcting it?
Let’s get started by understanding parallax, its causes and how to fix it.
What is parallax?
Parallax, as a term, is simple to understand. But how it relates to riflescopes is where things become difficult to understand.
Parallax is simply the difference or displacement in the apparent direction of an object when seen from two different points. This difference is usually not in a straight line.
Seems complicated? True.
But since we’re dealing with a rifle scope, maybe we define scope parallax. Here, parallax is the inconsistency or shift in reticle placement when you look through the scope at different angles.
Parallax causes the crosshair to move across the target as you shift the eye position. It simply means the reticle will not point directly where the rifle is aiming.
When using higher magnification scopes, you’ll likely see the reticle move off the target as you change your viewing angle. This movement of the reticle is what we call parallax.
You need to correct parallax to ensure accurate shooting when viewing from any angle.
Parallax is a common problem in higher magnification scopes. It also varies depending on the amount of magnification. The higher the magnification, the higher the parallax effect.
Shooters need to know how to adjust and compensate for parallax. You can easily detect it by moving your eye to change the viewing angle as you look through the scope.
Causes of scope parallax
For most shooters, scope parallax is never an issue at 250 yards or less. When you look through a scope, you’ll see the magnified target in the field of view. This is the area where all the light rays transmitted through the scope are focussed.
Your eyes see a projected image. Parallax will occur when the projected image is way too far. This can be on the front or behind the optic crosshairs.
To better understand parallax, take a sticker or a reticule on a kitchen window facing your garden. Now try taking a picture at the end of the garden. Where is the reticule pointed?
The reticule will change position depending on where you’re standing in the kitchen. This is a good example of exaggerated parallax.
Now repeat the same, but have the picture just behind the glass window, close to the reticule. Having the scope as close as possible to the picture ensures there is no room for movement.
Now take different positions in the room and look through the scope. No matter where you stand, the reticule will project to the same position. This is a good example of how to resolve parallax issues.
Generally, a scope’s reticle is usually placed on the first focal plane (FFP) or the second focal plane (SFP). A first focal plane reticle will vary in size, while a second focal plane reticle will remain static.
Let’s dive deep and understand how scope parallax adjustment is affected by the FFP and SFP.
First Focal Plane and second focal plane and parallax:
FFP sighting scopes are usually designed for long-range shooting. When adjusting an FFP sighting scope, the reticle size changes with changes in magnification.
The higher the magnification, the higher the parallax effect. In the context of a rifle scope, parallax refers to the apparent shift in the position of an object viewed through the scope when the position of the viewer’s eye changes. This can be a problem because it can make it difficult to get a precise aim on the target.
To mitigate this issue, many scopes have a parallax adjustment mechanism that allows the user to adjust the scope so that the parallax error is minimized at a given distance. This is particularly important at longer distances, where even small amounts of parallax error can have a significant impact on accuracy.
The first focal plane (FFP) refers to the location of the reticle (the crosshairs or other aiming points) in the scope. In a first focal plane scope, the reticle is located in front of the magnification lens, so when the magnification is changed, the size of the reticle also changes. This can be useful because it allows the user to use the same point of aim at any magnification setting.
On the other hand, in a second focal plane (SFP) scope, the reticle is located behind the magnification lens, so it remains the same size regardless of the magnification setting. SFP scopes are generally simpler and cheaper to manufacture, which is why they are more common in lower-priced scopes.
Examples of scope parallax
Here are a few examples of how scope parallax can manifest:
- When aiming at a target at a short distance, the point of impact may be higher or lower than the crosshairs, depending on the angle of the scope and the distance to the target.
- When aiming at a target at a long distance, the point of impact may be to the left or right of the crosshairs, again depending on the angle of the scope and the distance to the target.
- When the shooter moves their head slightly from the center of the scope, the point of impact may shift, even if the target is at the same distance. This is known as “movement parallax” and can be particularly problematic for long-range shooting.
To correct for scope parallax, the shooter can use the adjustable objective (AO) or side focus knob on the scope to fine-tune the focus of the scope and align the line of sight with the bore of the firearm. This will help to ensure that the point of impact is consistent with the position of the crosshairs at any given distance.
How to eliminate parallax in a scope
Scope parallax can be problematic because it can cause shots to be placed inaccurately. Here are a few ways to eliminate or reduce parallax in a scope:
- Use a scope with a parallax adjustment feature: Many high-end scopes have a parallax adjustment knob or lever that allows the shooter to adjust the focus of the reticle to eliminate parallax.
- Use a scope with a fixed parallax: Some scopes are designed with a fixed parallax, which means that the reticle is always in focus at a specific distance. This can be beneficial because it eliminates the need for parallax adjustment, but it may not be suitable for all shooting situations.
- Adjust your shooting position: When shooting at long distances, it is important to have a stable shooting position. This can help to minimize the amount of movement in the scope, which can reduce the appearance of parallax.
- Use a higher magnification: Higher magnification scopes can help to reduce the appearance of parallax because they make the target appear larger and closer. However, high magnification can also make it more difficult to acquire the target quickly.
- Use a reticle with MOA or MIL markings: Reticles with MOA or MIL markings can be used to make adjustments for windage and elevation, which can help to compensate for parallax.
By following these tips, you should be able to eliminate or reduce the amount of parallax in your scope.
Big mistakes shooters and hunters make on scope parallax
One common mistake that shooters make regarding scope parallax is failing to adjust the parallax setting for the distance of the target. This can lead to shots that are off-target because the shooter was not properly aligned with the reticle.
Another mistake is assuming that all scopes have adjustable parallax. Some scopes, particularly lower-priced ones, may not have this feature. In these cases, the shooter must be extra careful to ensure that their eye is properly aligned with the scope.
Shooters may also make the mistake of believing that the parallax adjustment on their scope is a substitute for proper sight alignment. While adjusting the parallax can help to improve accuracy, it is not a replacement for proper sight alignment and trigger control.
Finally, some shooters may not fully understand how parallax works or how to adjust it, leading to incorrect usage of the feature. It is important for shooters to understand the principles of parallax and how to adjust for it in order to get the most out of their scope.
Why is Parallax Important?
Overall, parallax is important when shooting at small targets. When hunting big games, parallax might not be a huge problem. When not adjusted, shooters might get a shot a few inches from the aimed spot.
For ethical hunting, you don’t want to leave the game injured. You need a precise shot at vital organs for an immediate kill.
You need the target and the reticle to be on the same focal plane. Almost all long-range scopes are designed with a parallax adjustment. This can be in the form of a turret on the side of the scope or a ring on the objective lens.
Travis Mike is a firearm enthusiast and author passionate about all things guns. With 10 years of experience in the industry, Travis Mike has gained a wealth of knowledge on the subject. He is skilled in gunsmithing and tactical training. In addition to professional experience, Travis Mike is an avid hunter and shooter, regularly participating in local shooting ranges and hunting trips.