What Is Parallax On A Scope? (Explained For Beginners)

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Parallax is one of the most difficult things to understand about shooting. Many people think it’s nothing more than getting the reticle to focus on the object, but there’s a lot more to it than that.

Understanding parallax is essential for shooting, especially in situations when accuracy is important. If you’re competing in a sporting competition that requires you to hit a target at 500 yards or hunting at long range, you need to know about parallax and how to correct for it.

What is parallax?

To understand what parallax is, it helps to start by understanding what it looks like when you see it.

Parallax is when you look through your scope and see the reticle or crosshairs moving around instead of focusing on the object you’re aiming for. The crosshairs might seem to hover or float around over your field of view or create an odd 3D effect.

Depending on how well you line up your aim and adjust for this phenomenon, parallax can cause you to miss your shot.

Generally, parallax is the effect of an object seeming to change position relative to more distant objects. It’s caused by a change in the line of sight and is a bit of an optical illusion. But, on a rifle scope, it does have a cause. Parallax occurs when the focal plane of your target is not the same as that of the reticle or crosshairs. That might be a little hard to understand, but what it means is this: you can fix parallax on a scope.

Thinking about how parallax appears in real life can help you understand it a little better.

Put simply, parallax is when objects seem to move when viewed from different positions. One easy way to see this is to put your hand up in front of your face, then alternate opening and closing each eye. Your hand appears to shift from left to right, depending on what eye is open, but it’s not actually moving at all. Your eyes are just seeing it from different angles.

Another example is when you’re looking out the window of a moving car. The utility poles and guard rails close to the car seem to fly by while the trees in the distance move slowly. Or, if you’re in the passenger seat and look over at the speedometer, you can’t really tell how fast the car is traveling. The angle and the distance between you and the dashboard make it impossible. The driver, on the other hand, can look at the dial and know the precise speed.

What does the parallax setting do on a scope?

The parallax setting on a scope adjusts to correct the discrepancy between the focal planes of the target and the reticle. In simple terms, the parallax setting eliminates the optical illusion, putting everything on the same plane.

Parallax is usually not noticeable at short range or when using scopes with low magnification. That said, if you’re trying to make a long-range shot, parallax is a significant problem that affects your accuracy.

What is a parallax error in a rifle scope?

A parallax error occurs when you see this optical illusion when looking through your scope. So, when you change the angle you’re looking through the scope or shift your eyes, the reticle will shift relative to the target. It usually seems like it’s hovering and slowly moving around the frame, but it can create a 3D effect, too.

As mentioned, parallax occurs because the target and the reticle are on two different focal planes. Sometimes, it can seem like everything is lined up correctly when you’re looking at your target straight on, but things start to shift when you move your head or the target walks to another area of your field of vision.

The fact that parallax can appear seemingly out of nowhere when you shift your focus is part of the reason why it is so important to correct for it when shooting. You might take aim thinking that things are fine, but when your prey moves farther away, parallax makes it really difficult to make an accurate shot.

Why is parallax important?

Parallax is important because it has a big effect on accuracy, especially when using scopes with high magnification or shooting at long range. You might think that everything is just fine with your scope. You locate your target and line up your shot, only to see the reticle seem to float out of place or shift right before you pull the trigger.

If you’re aiming at a target in a competition or trying to make a kill shot on something from a long distance, parallax can be the difference between whether you get your shot or not.

Does parallax affect accuracy?

Yes, as mentioned, parallax does affect accuracy, sometimes significantly so. What’s worse is that it can, at times, seem to come out of nowhere.

That said, how much parallax affects accuracy depends on a few things. The more magnification your scope has, the worse parallax is. Because of this, most high-powered scopes have a parallax adjustment.

With less magnification, the illusion usually isn’t that bad. In fact, you might not notice it at all. Most short-range scopes either do not have a parallax adjustment or are fixed. Fixed parallax means that the scopes are pre-adjusted and the changes are locked in place.

Does the focal point affect parallax?

Yes, the focal point affects parallax significantly. Remember the example of the utility poles and trees passing the window in a moving car? If you focus on the utility poles and guard rails that are closer to the car, they seem to move fast. But, if you shift your focal point to the trees, they seem to move slowly.

Remember that in a scope, parallax results from the crosshairs and the target being on different focal planes. If you shift your focal point from the target to another area in your field of vision, it changes everything.

Depending on the magnification of your scope and what you’re looking at, parallax may be unnoticeable when the focal point is closer and directly in front of you. But, when you focus on something farther away or even move your eyes to another area of your visual field, parallax can be significant.

How to set parallax on a scope

If you have a scope with a parallax adjustment, here’s a basic rundown of how to set it.

First, make sure the safety is on. Then, look through the scope and line up the crosshairs on something small and about 100 or 150 yards away. Make sure you adjust the diopter and the magnification so you get as clear a view as possible.

Hold the rifle as still as possible, using a rest or stand if necessary. Move your eye around without removing it from the scope, looking from one side of your visual field to the other. Try focusing on things that are close to you and then shifting to things that are farther away. If the crosshair moves as your eyes move, you know that it’s time to adjust for parallax.

To make these changes, move the adjustment knob all the way out, then slowly adjust it back. Watch your target and move your eyes slightly to continue to check for parallax. When you no longer see the illusion, stop.

Depending on the type of rifle you have, you may have to readjust when changing the magnification. Generally, the higher the magnification, the more likely it is that you’ll experience parallax. Take your time to make the proper adjustments. Even the slightest parallax can affect your aim.

It’s worth noting that your experience may vary depending on whether you’re dealing with a first focal plane (FFP)  scope or a second focal plane (SFP)/rear focal plane scope (RFP). These terms define where the reticle is.

On an FFP scope, the reticle is located in front of the magnification lens. As you adjust the scope, the reticle grows and shrinks as you adjust the magnification on an adjustable range scope. (On a fixed range scope, it will always look the same size.)

With SFP or RFP scopes, the reticle is behind the magnification lens, meaning that it always stays the same size, regardless of the magnification power.

What does this mean for adjusting parallax? Since the size of the reticle changes with an FFP scope, you must be more precise with parallax adjustments.

Setting for varying distances

After you adjust for parallax, you can’t just assume that you’re set and won’t need to make any more adjustments. If you change the magnification or shift your focal point to something farther away, it’s bound to happen again.

Ideally, you should adjust parallax every time the distance between you and your target varies significantly. That said, there’s no hard and fast rule about when or how often to do so. For example, if you adjust parallax at 75 yards for a target that’s at 100 yards, you might still be okay for a target that’s at 150 yards. It all depends on the type of rifle scope you choose for your particular needs.

That said, no matter how high-quality your scope is, at a certain point, you’ll have to readjust. It’s safe to say that if you come across a target that’s, say, 500 yards away, and you adjusted for 100 yards, it’s time to make some changes.

In most cases, you’ll get to know your scope and what you need to do in various conditions. If you know your scope is generally pretty good after that first adjustment up to 250 yards, you may not need to adjust parallax very often. But if you notice the effect at closer to 200 yards, make a point to adjust it to ensure you get accurate aim.

Is parallax the same as focus?

Parallax is not the same as focus, though many people confuse the two.

If your focus is off, it’s a physical problem that you can fix by adjusting the lenses. Parallax, on the other hand, is an optical illusion.

Going back to the example about riding in the car and looking out the window as things pass by. If you’re wearing glasses or contact lenses, they are correcting your focus. But you will still experience parallax as the things out the window seem to pass at different speeds.

When you adjust for parallax, it doesn’t affect the focus at all. What it does is move the focal planes to eliminate the effect of the reticle moving around your field of vision.

Do all scopes have parallax adjustment?

No. Some scopes have a fixed parallax, which is usually set for about 100 to 150 yards or so, though can go all the way up to 400 yards. Although these are effective in some situations, many hunters prefer an adjustable parallax. If you regularly shoot at things farther than 100 or 150 yards away, you can see why having an adjustable parallax is useful.

What is parallax corrected?

A parallax corrected scope is a scope without a parallax adjustment knob. It’s basically another name for a scope with a fixed parallax and indicates that the manufacturer took measures to correct any issues. As mentioned, scopes that have a fixed parallax or are parallax corrected are usually set for about 100 or 150 yards.

What does parallax free mean?

Parallax free means that there is no parallax, that you’ve eliminated the optical illusion. Parallax free or fixed parallax scopes are locked in place for the amount of magnification of the scope. A parallax free scope is fine for hunting between, say, 100 to 400 yards at the most. If you’re aiming at something farther away or target shooting for a sports competition, a parallax free or fixed parallax scope is not ideal.

Do you need a rifle scope with a parallax adjustment?

It depends on what type of hunting you’re doing. Parallax is rarely an issue at anything less than 100 to 200 yards or so. If you’re shooting at targets in close range, a parallax adjustment isn’t really necessary.

That said, if you shoot in different conditions or locations or if you regularly compete in sporting competitions where accuracy is important, an adjustable parallax is essential. Without one, you run the risk of losing a significant amount of accuracy on long shots.

Do you need parallax adjustment for hunting?

It depends on what you’re hunting. If your prey is within 100 yards or so, you don’t really need to worry about parallax. But, if you’re planning to change between a variety of distances or shoot at long range, parallax adjustment is the only way to make sure you’re shooting as accurately as possible. Check out our article: How To Choose A Rifle Scope For Deer Hunting.

Final Thoughts

Parallax can be a difficult concept to understand. I hope that our real-world examples and the explanations I provided here help you get a better grasp of what it is and why it’s important for accuracy.

Whether you need a scope with an adjustable parallax or one that’s fixed is up to you. Generally, scopes with high magnification perform better with adjustable parallax. That said, parallax is not usually a problem at close range. If you usually shoot at short range, say, less than 100 or 150 yards, a fixed parallax is probably fine.