Parallax

Parallax is an axis, a term that refers to an instrument error, most commonly a riflescope when aiming at a close or distant object. It occurs due to the incorrect position of the eye with respect to the riflescope in terms of both distance and the optical axis. Almost all gun manufacturers sight rifles at a distance of 100 meters. Rifle scope manufacturers have naturally followed suit and therefore typically set the parallax at 100 meters. Such riflescopes are marked as – parallax-free at 100 meters. So if we shoot at 100 meters, we don't have to consider parallax at all, not even in terms of eye position. This is because, if we have the eye in the ideal position relative to the riflescope, that is, at the correct distance and directly on the optical axis, the effect of parallax is not observed at all. Unfortunately, nothing is ideal, right?

The effect that causes us to miss the target

To better understand the effect of parallax, let's try to explain it. Imagine a point of unchanging position, point A (the riflescope). Furthermore, somewhere in front of it, at a relative distance, there is a target, labeled C. This target has its unchanging position. If we look through point A at the ideal angle, we will see target C in its place. However, if our eye moves in axes X, Y, Z, the line of sight through point A shifts the position of target C in a reverse manner. Therefore, the target will never be where it actually is. The shooter is thus shooting elsewhere than where the target is located. Now imagine that the riflescope, that is, the rifle, is not ideally positioned. It moves in the hands, and we breathe, etc. For a target that is 200-300 meters away, if the image in the riflescope is displaced by 0.164mm, it can result in a point of impact being off by 3.7cm. Many will now argue – that's a smaller error than the accuracy of the ammunition, weapon, or even the shooter. Yes, you're right.

Many riflescopes, especially the higher-quality ones, have the ability to adjust the parallax. This allows the error to be corrected and becomes irrelevant. A small tip – when aiming, try to keep the image clear, so that the edges of the riflescope do not shadow. Such advice is only partially effective, but better than nothing.

Interestingly, sport shooters are able to utilize the influence of parallax. Through it, they estimate the distance of the object they are aiming at. If the weapon is firmly mounted, the distance can be determined using parallax. More or less – gently moving the eye relative to the riflescope axis while adjusting the distance. The moment the target stops "traveling" in the riflescope, the distance is correct. You just need to read it.

In conclusion…!

Parallax is therefore an optical error that occurs due to the imperfect positioning of the eye relative to the optical axis. Let's not be hard on ourselves; unfortunately, it cannot be done perfectly. If we are hobby shooters who shoot airguns in the backyard, we don't need to worry about parallax. However, with increasing levels of shooting, it becomes necessary to purchase such a riflescope that can influence parallax by adjusting its internal mechanisms. Remember, such internal adjustments occur within tenths and hundredths of a millimeter. Therefore, it is necessary to purchase a quality riflescope, for example, from Swarovski or NightForce.