Rifle Scope Parallax Definition

Table Of Contents

Parallax is one of the least understood terms in the niche of sport hunting and shooting.

Even firearm hobbyists and experienced shooters get confused about the rifle scope parallax definition.

In this guide, you’ll learn the essentials of parallax.

We’ll also show you some common parallax issues and how to correct them, and whether you need a rifle scope with parallax adjustments.

What Is Parallax?

When aiming your rifle using a scope, you want your reticle and the target to be on the same focal plane.

When they’re not, you experience a phenomenon called parallax.

It’s detectable when you look through the scope and the reticle moves or swims around the object you are aiming at.

In a simple definition, parallax is a noticeable shift in the reticle as you look through your rifle scope at different angles.

For example, if you notice that the reticle is moving off target while you change your viewing angle, you are dealing with parallax.

Parallax on Rifle Scopes

Rifle scope parallax is more like an optical illusion.

It makes the target look out of focus when you change your viewing angles or move your head while looking through the scope.

Scope parallax usually occurs at a high level of magnification.

Two scenarios may lead to parallax.

One, your target image and the retina center are not on the same focal plane.

Two, your scope is out of focus when you’re looking through it.

For short-distance shooting, parallax isn’t a problem.

That’s because most standard rifle scopes are parallax-corrected up to a certain range, typically within 150 yards or less.

However, most scopes made for long-range shooting will need to be adjusted to eliminate parallax and get your target and reticle on the same focal point.

Another situation in which parallax can become an issue is when you have a scope dialed in high power, but your target is within a short range.

What Causes Parallax in Rifle Scopes?

Parallax occurs when the reticle and the target are on different planes within the scope.

When shooting at longer distances or over 150 yards, your brain adjusts your vision’s focal length to compensate for the target’s distance.

As a result, the reticle will appear slightly out of focus or shift when you adjust your viewing angle.

When this happens, or when your reticle moves off target, your point of impact will follow.

At short distances, parallax doesn’t affect the accuracy of your aim.

Simple animation demonstrating the effects of parallax compensation in telescopic sights as the eye moves relative to the sight. See how the bottom picture appears locked onto your aiming point or target, even if you tilt your head or shift your viewing angle.

What Is Parallax Adjustment?

Adjusting parallax is critical to ensure accurate shots.

If the reticle and the target image aren’t on the same focal plane, either one can appear out of focus when you look through your scope.

As a result, you’re more likely to miss a shot.

As we mentioned earlier, parallax can occur in two different optical illusions:

The image of your target is clear, but the reticle is out of focus.
The image is clear when looking head-on, but the reticle moves to the right or left when you move your head or look through the scope at a different angle.

How Do You Fix These Parallax Errors?

Below are some of the things that you can do to fix any parallax issues.

Get Your Reticle in Focus

Before attempting to adjust for parallax, it’s important to make sure that your reticle is in focus.

There are many reasons your scope might seem out of focus.

The first and most common reason is that your scope’s exterior lenses could be dirty.

Like most types of glass, rifle scope lenses can quickly attract foreign substances, even fingerprints.

Over time, foreign materials can build up on the surfaces of your exterior lens and will eventually impair its clarity.

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They can make your scope appear blurry when you look through it.

You should clean the lens using wipes specially made for glass, along with a scope brush.

A scope brush is a small tool with a fine and felt-tipped flatter brush.

Meanwhile, a dry lens pen can help get rid of the smudges and fingerprints on the lens.

Set the Ocular Focus Properly

Even if the lens is clean, if the ocular focus of your scope is set improperly, it can trigger parallax.

Most rifle scopes feature either a standard ocular focus or a fast focus setup.

Scopes that utilize a standard focus involve a mechanism where the entire eye box rotates to focus.

Meanwhile, scopes that feature fast focus come with an ocular ring used to adjust the eye box focus.

If you’re using this kind of scope, you should adjust the eye box focus by shouldering your unloaded rifle, and pointing the muzzle up toward the blue part of the sky.

Alternatively, you can point your gun to a blank backdrop, such as a wall.

This is so that when opening your dominant shooting eye, you’ll look at a light background without any distractions.

Next, very quickly focus on the reticle to see if it appears in focus.

If the reticle is out of focus, turn the eye box, or the ocular ring left or right.

Then adjust the eye box focus to test against the blue sky or wall.

Continue rotating the ocular focus left or right and testing it until the reticle is in focus when you first open your eye.

rifle scope parallax definition and tips

Adjust for Parallax

A while ago, we said that modern rifle scopes are usually built with a focus feature that’s either fixed or adjustable.

However, do note that focus is not the same as parallax, but the two features are related as either one can impact the clarity of your target as you look through the scope.

Let’s talk about the different types of focus and how each one plays a role in the scope being blurry.

Fixed Focus or Parallax

Short-range rifle scopes often have a non-adjustable focus and a pre-set parallax.

Now, a scope with a fixed focus will provide the best image quality at its pre-set parallax setting.

For example, if you’re using a rifle scope with a parallax set at 50 yards and looking at a target 30 yards away, you can’t expect a clear image.

A rifle scope without parallax adjustment is pre-set to be parallax-free at a specific distance.

At that distance, you can move your head or eyes in different directions or angles.

Also, the crosshairs won’t move to your target.

Below are the different types of rifle scopes and the pre-set parallax adjustments:

Rifle Scope: 100 to 150 yards
Rimfire Scope: 50 to 100 yards
Air Gun Scope: 50 to 75 yards

Adjustable Focus or Parallax

With this type of rifle scope, you can adjust the focus or parallax either through an adjustment assembly on the ocular bell or via a side focus feature.

This means that if your target is 50 yards away, you will need to set the parallax at 50 yards to see through the scope with the highest clarity.

Some rifle scopes come with adjustable parallax.

This innovative feature is designed to improve shooting accuracy.

Often, adjusting for side focus is done by moving the reticle’s plane to the same distance as the image.

Take note that the point of impact for the bullet changes every time you make adjustments on the focus or parallax.

Thus, you should mark which direction to turn on the turret when adjusting the reticle or adjust the parallax setting each time you change the shooting range of your scope.

How To Adjust for Parallax

Needless to say, parallax adjustment is one of the most important features to look for when shopping for a rifle scope.

Different brands and models will have varying mechanisms of adjusting for parallax.

Most modern rifle scopes will have a parallax adjustment system in a form of a dial.

The dial is usually found on the side of the main tube, also called the side focus.

Most of the dial systems used in adjustable rifle scopes are marked with yardage in increments of 50 or 100 yards.

The easiest way to find the adjustment dial’s correct position is by setting up a clear target that will stand out well against the background.

Here are what you need to do:

Get your rifle in a secure rest position.
Next, set the magnification of your scope to its highest level.
At this point, you can now look through the scope and begin to shift your head back and forth.
If your reticle appears to move or shift as you move your head, you have a parallax issue. Parallax adjustment dials have yardage indicators for easy reference.
Depending on your range and the magnification level of your scope, adjusting the parallax may involve fine-tuning to a full revolution of the dial.

You know you’ve adjusted the parallax correctly when you see that your reticle is sharp against your target.

It should also appear locked onto your aiming point or target, even if you tilt your head or shift your viewing angle. (See the picture above)

If you have made your adjustments but continue to see even a minor parallax issue, continue making fine corrections.

Some rifle scopes make use of a ring-style system when adjusting for parallax.

This mechanism is also easy to use, but it may not be as precise as the dial type with yardage indicators.

Tips When Adjusting for Parallax

While it may sound cumbersome, you need to adjust your scope’s parallax setting for every range.

To make things easier, keep notes on paper of your shooting ranges and parallax adjustments so you have something to refer to the next time you deal with the same distance or range.

For example, once you know your parallax dial should be set at the 80-yard mark for a target at 100 yards, you won’t have to keep testing over again.

Lastly, remember that in most adjustable scopes, you can adjust the parallax setting to infinity.

Since there is no one-fits-all setting for parallax, you have to keep adjusting until you see the image crisp and clear and your reticle is locked on it.

Ensure your stance, head, eye, and cheek placement are consistent every time you adjust for parallax.

Sight pictures can get blurry as you change magnifications while adjusting for parallax.

Calibrating the side focus helps ensure a sharp and crisp image while correcting parallax.