Measuring shooting distance with parallax correction, or What is parallax? What is parallax, and why is it necessary to adjust it in optical sights What is parallax on an optical sight

You are on a train and look out the window... Posts along the rails flash by. Buildings located a few tens of meters from the railway track run back more slowly. And already very slowly, reluctantly behind the train, houses, groves that you see in the distance, somewhere near the horizon ...

Why is this happening? This question is answered in Fig. 1. While the direction to the telegraph pole changes by a large angle P 1 when the observer moves from the first position to the second, the direction to the remote tree will change to a much smaller angle P 2 . The rate of change of direction to the object during the movement of the observer is the less, the farther the object is from the observer. And from this it follows that the magnitude of the angular displacement of an object, which is called the parallactic displacement or simply parallax, can characterize the distance to the object, which is widely used in astronomy.

Of course, it is impossible to detect the parallax displacement of a star moving along the earth's surface: the stars are too far away, and the parallaxes during such displacements are far beyond the possibility of measuring them. But if you try to measure the parallactic displacements of stars when the Earth moves from one point of the orbit to the opposite one (i.e., repeat observations with an interval of half a year, Fig. 2), then you can quite count on success. In any case, the parallaxes of several thousand stars closest to us have been measured in this way.

Parallax shifts measured using the Earth's annual orbital motion are called annual parallaxes. The annual parallax of a star is the angle (π) by which the direction to the star will change if an imaginary observer moves from the center of the solar system to the earth's orbit (more precisely, to the average distance of the Earth from the Sun) in a direction perpendicular to the direction to the star. It is easy to understand from Fig. 2 that the annual parallax can also be defined as the angle at which the semi-major axis of the Earth's orbit is visible from the star, located perpendicular to the line of sight.

The basic unit of length, adopted in astronomy for measuring the distances between stars and galaxies, is also associated with the annual parallax - the parsec (see Units of distances). The parallaxes of some nearby stars are given in the table.

For closer celestial bodies - the Sun, the Moon, planets, comets and other bodies of the Solar System - the parallactic displacement can also be detected when the observer moves in space due to the daily rotation of the Earth (Fig. 3). In this case, the parallax is calculated for an imaginary observer moving from the center of the Earth to the point on the equator at which the luminary is on the horizon. To determine the distance to the luminary, calculate the angle at which the equatorial radius of the Earth, perpendicular to the line of sight, is visible from the luminary. Such parallax is called diurnal horizontal equatorial parallax or simply diurnal parallax. The daily parallax of the Sun at an average distance from the Earth is 8.794″; the average daily parallax of the moon is 3422.6″, or 57.04′.

As already mentioned, annual parallaxes can be determined by direct measurement of the parallactic shift (the so-called trigonometric parallaxes) only for the nearest stars located no further than a few hundred parsecs.

However, the study of stars for which trigonometric parallaxes have been measured has made it possible to discover a statistical relationship between the type of a star's spectrum (its spectral type) and the absolute magnitude (see the "Spectrum-luminosity" diagram). By extending this dependence also to stars for which the trigonometric parallax is unknown, they were able to estimate the absolute stellar magnitudes of stars by the type of spectrum, and then, comparing them with apparent stellar magnitudes, astronomers began to estimate the distances to stars (parallaxes). Parallaxes determined by this method are called spectral parallaxes (see Spectral classification of stars).

There is another method for determining distances (and parallaxes) to stars, as well as star clusters and galaxies - by variable stars of the Cepheid type (this method is described in the Cepheid article); such parallaxes are sometimes called Cepheid parallaxes.

Many questions arise in hunting circles about this word. Novice hunters who have waited for the "pink" buy a rifled carbine and optics to follow it, but not everyone understands technically how to install an optical sight, how to shoot, and even how to choose the right optical sight, let alone the complex concepts of the sight itself and how to work with it. After a certain time, experience and "bumps" on the head, a novice hunter or shooter becomes a specialist or professional. But in a hurry, or for joy, they buy an optical sight, and then with disappointment they want to return it back, due to lack of information or insufficient consultation on this narrow issue ...

I have a bad sight, it is out of focus, a bad image, you can’t clearly see anything, etc....hearing or reading fragments of information about the need for a sight with parallax SETUP, that it is very necessary for him, or that it is best . Let's try to open this topic a little, once again.

Let's turn to the network: PARALLAX or PARALLAX ERROR.

Wikipedia briefly tells us what parallax is and the types of parallax.
Parallax(Greek παραλλάξ, from παραλλαγή, “change, alternation”) - a change in the apparent position of an object relative to a distant background, depending on the position of the observer.
Types of parallax: Temporal - Daily, Annual, Century, parallax in the Photo (Viewfinder), Stereoscopic and Rangefinder parallax. OUR topic includes the parallax of the video scanner (sight) - this is not the height of the axis of the sight above the axis of the barrel, but the error in the distance between the shooter and the target.

What do they write on third-party sites that are close to our subject?

Parallax is the apparent movement of the target relative to the reticle as you move your head up and down when you look into the scope's eyepiece. This happens when the target does not hit on the same plane as the reticle. To eliminate parallax, some scopes have an adjustable lens or wheel on the side. The shooter adjusts the front or side mechanism while looking at both the reticle and the target. When both the reticle and the target are in sharp focus, with the scope at its maximum magnification, the scope is said to be free of parallax.

Parallax called the apparent shift of the target image in relation to the image of the aiming mark, if the eye moves away from the center of the eyepiece. This is due to the fact that the image of the target is not exactly focused in the focal plane of the reticle.

Parallax the apparent displacement of the observed object due to the movement of the shooter's eye in any direction is called; it appears as a result of a change in the angle at which the given object was visible before the shooter's eye moved. As a result of the apparent displacement of the aiming pin or cross hairs, an aiming error is obtained, this parallax error is the so-called parallax.

From all this it is clear that scope parallax- This is the value associated with the focus of the sight. Simply put, when YOU are looking into an optical sight that is aimed at some object, and when the head (axis of the eye) moves, the crosshair deviates from the aiming point, moves along the target. It can also be said that sight parallax is the internal focusing of the sight on some object at a certain distance.

Everyone who has ever photographed has encountered the parallax effect.. When you photograph, for example, friends against the background of some object (a monument) that is at a decent distance from you and your friends, and the camera focuses either on friends or on a monument ... then you get a photo, either with friends in focus and a blurry monument, or with a monument in focus but blurry friends, especially if you have a camera lens with a large depth of field. The principle of focusing the camera lens is based on the focusing of the human pupil. When photographing, you get two planes friends and a monument, if you move a little or sway from side to side, then the planes will shift relative to each other and you. If friends come close to the monument (they stand in the same plane), then the focus will be the same, i.e. if you move (change position), then the focus will not change and there will be no "OUTFOCUS", and the photo will be clear with all participants.



So in the sight you also have two planes, a plane with a crosshair, and a plane with a target, and in the role of a camera your pupil, if you focus on the target, then the crosshair will not be clear, if you focus on the crosshair, then the target will be washed out, as if not focused. It is necessary to ensure that the crosshairs and the target are in clear focus, and when your pupil moves, the planes of the target and crosshairs do not move relative to each other, i.e. the crosshair did not move on the target.


First you need to talk about sights. Sights are divided into two types, with parallax detuning and without detuning.

Riflescopes without parallax adjustment have an internal focusing of the lens at a distance of about 100 meters (90-150m), or as they say with a fixed parallax at 100 yards or meters. In such sights, the target plane is ideally focused at a distance of 100 meters from the shooter, and when the head is nodding, the crosshair is stationary. If the target is moved to a distance of 40 meters, or 300-400 meters, then you will also see the reticle in focus, but the target is a little blurry, and when you nod your head, the crosshair will move a little.


Basically, there is no parallax adjustment in sights for shooting at short and medium distances, where shooting is meant at distances up to 600-800 meters. In hunting scopes, for standard hunting ... shooting at distances up to 300-500 meters is already considered decent, and parallax adjustment is not needed at all. Why? Because the bullet deviation error at the maximum parallax error at such distances is measured in millimeters, more precisely 20-40 mm deviation of the bullet from the aiming point. The objects of modern hunting are much larger in size, and even with the maximum parallax error, you will fall into the kill zone of any animal at a distance of 400-500 meters. The only discomfort may be in the perception of the target, the further the object of fire is, the worse the clarity, even at maximum optical magnification.

Scopes with parallax adjustment have an additional drum on the control unit or a ring on the lens. Such a drum (parallax adjustment drum) is usually located on the left side of the sight settings node, but it can also be on top, it is called ( SF- Side Focusing - side focusing). Additional accessories are installed on it, for fine-tuning the focus, in the form of rings of different diameters.


The parallax adjustment can be located on the scope lens, in the form of a wide ring, such a ring is called ( AO- Adjustable Objective - an adjustable target or an adjustable lens), but sometimes the abbreviation (AO) simply refers to the presence of an internal focusing lens setting.
Sights with parallax adjustment are designed for shooting at long and ultra-long distances, when the accuracy of the shot is affected by every millimeter of parallax adjustment, wind correction, atmospheric pressure, ambient temperature, altitude and much more. Shooting at such distances is more sports than hunting, well, or a sniper's prerogative. Of course, there are also hunting scopes with parallax adjustment, especially for hunting on the plains or in the mountains, when hunting without powerful optics (binoculars, tubes, rangefinder, sight) is unthinkable, and sometimes you prepare for an accurate shot for more than one hour.

On Lens (AO)

On Lens (AO)

On the settings node (SF)

On the settings node (SF)


In inexpensive collimator sights parallax fixed at 40-50 meters, since aimed shooting with the help of these sights is carried out at a limited distance of up to 100 meters. If you take collimator sights for rifled weapons, then the parallax effect is usually absent or reduced to a minimum error (Aimpoint and EOTech), and you can shoot accurately at a distance of more than 100 meters.

Parallax in collimator sights, is also present, but this topic is more relaxed, unlike optical sights. There is no parallax adjustment in the collimators, it is either absent or fixed, it all depends on the brand. Here the question of functionality comes to the fore, why do YOU ​​need a red dot sight? For pistol, shotgun, or rifled carbine.

In the conversations of the "experienced", when it comes to optical sights, the concept of "parallax" often "pops up". At the same time, many companies and models of sights are mentioned, and various assessments are made.

So what is parallax?

Parallax is the apparent shift of the target image in relation to the image of the aiming mark, if the eye moves away from the center of the eyepiece. This is due to the fact that the image of the target is not exactly focused in the focal plane of the reticle.
Maximum parallax occurs when the eye reaches the scope's exit pupil. But even in this case, a sight with a constant magnification of 4x, detuned from parallax by 150 m (at the factory) will give an error of about 20 mm at a distance of 500 m.
At short distances, the parallax effect practically does not affect the accuracy of the shot. So, for the sight mentioned above at a distance of 100 m, the error will be only about 5 mm. It should also be borne in mind that when keeping the eye in the center of the eyepiece (on the optical axis of the sight), the parallax effect is practically absent and does not affect the accuracy of shooting in most hunting situations.

Riflescopes with factory parallax adjustment

Any sight with a fixed lens focusing system can only be adjusted from parallax to any one specific distance. Most scopes are factory set to 100-150m parallax.
The exceptions are low magnification sights, oriented for use with a shotgun or combined weapons (40-70 m) and the so-called "tactical" and similar sights for shooting at long distances (300 m or more).

According to experts, you should not pay serious attention to parallax, provided that the shooting distance extends within: 1/3 closer ... 2/3 farther than the distance of the factory detuning of the sight from parallax. Example: "tactical" scope KAHLES ZF 95 10x42 is parallax-free at the factory at a distance of 300 m. This means that when shooting at distances from 200 to 500 m you will not feel the effect of parallax. In addition, when shooting at 500 m, the accuracy of the shot is affected by a lot of factors related primarily to the characteristics of the weapon, the ballistics of the ammunition, weather conditions, the stability of the position of the weapon at the time of aiming and firing, leading to a deviation of the point of impact from the aiming point by , significantly exceeding the deviation caused by parallax when firing a rifle clamped in a vise in absolute vacuum.
Another criterion is that the parallax does not show up significantly until the magnification factor does not exceed 12x. Another thing is sights for target shooting and varminting, like, say, 6-24x44 or 8-40x56.

Riflescopes with parallax adjustment

Target shooting and varmint require maximum aiming accuracy. To ensure the required accuracy at different shooting distances, sights are produced with additional focusing on the lens, eyepiece or on the central tube body and the corresponding distance scale. Such a focusing system allows you to combine the image of the target and the image of the aiming mark in one focal plane.
To eliminate parallax at a selected distance, do the following:
1. The image of the aiming mark must be clear. This must be achieved using the focusing mechanism of your scope (diopter adjustment).
2. Measure the distance to the target in some way. By turning the focusing ring on the lens or the handwheel on the body of the central tube, set the measured value of the distance opposite the corresponding mark.
3. Securely fix the weapon in the most stable position and look into the scope, concentrating on the center of the reticle. Raise and then lower your head slightly. The center of the aiming mark must be absolutely stationary in relation to the target. Otherwise, perform additional focusing by rotating the ring or drum until the movement of the center of the mark is completely eliminated.
The advantage of scopes with parallax adjustment on the center tube body or on the eyepiece is that when adjusting the scope, the shooter who is ready to shoot does not need to change position.

Instead of output

Nothing just happens. The appearance of an additional adjustment unit in the sight cannot but affect the overall reliability of the design, and, if properly executed, the price. In addition, the need to think about additional adjustment in a stressful situation cannot but affect the accuracy of your shot, and then you yourself, and not your sight, will be to blame for the miss.

The above values ​​are taken from materials provided by companies (USA) and (Austria).

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The World Hunting Technologies company is the official representative of Kahles, NightForce, Leapers, Schmidt&Bender, Nikon, AKAH, Docter optical sights on the territory of the Russian Federation. But in our assortment you can find sights from other well-known manufacturers. All scopes sold by us carry a full manufacturer's warranty.

Modern optical sights for all types of hunting, sporting, benchrest, varmint, sniping, tactical use and for installation on pneumatics. Sale, selection of brackets, installation and warranty (post-warranty) maintenance of optical sights in St. Petersburg and throughout Russia!

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Let's leave aside the physics of the phenomenon of parallax (for those who are interested, they will find where to read about it). The main thing is that it exists and complicates the life of fans of pneumatics and crossbows. Not only is it inconvenient to aim, but also accuracy suffers greatly.

This is how the shift of the point of impact looks like when classic parallax “moons” appear.

Where does it come from, who is to blame and what to do?

This is due to the desire of airgunners and some shooters from crossbows to acquire "cool" telephoto sights of high magnification. It is they who, at short (characteristic for this weapon) distances, are extremely susceptible to the appearance of moons, the image floating away, etc. And it is on them that manufacturers have to resort to complicating the design by introducing mechanisms for detuning from parallax (focusing). Both according to the simple AO technology (on the lens), and high-class SF (the detuning flywheel sometimes is a real steering wheel on the side of the sight).

Why the hell on a crossbow or a conventional pneumatic spring-piston rifle designed for “plinking” or hunting, a 9 or even 12x scope? Okay, with high-precision shooting, carried out from the stop and even the machine. When shooting from hand, often offhand, we, in addition to parallax, get a cross jumping over a huge target and the resulting desire to “catch” its center, which is one of the main aiming errors. But for some reason, this problem is not very relevant for firearms.

How does it look like with a rifled firearm, for which, in fact, the OP was originally intended? Firstly, shooting is carried out at distances from 100, well, even from 50 meters, at which parallax is no longer observed. Secondly, the multiplicity of army and hunting samples, as a rule, is small. Sniper scope PSO-1 (SVD) has 4x24 characteristics.

I (not on pneumatics) have its more modern “civilian” version 6x36, and its acquisition is caused by age-related visual impairment. Here, the lens aperture is higher due to the larger aperture, but most importantly, there is a diopter adjustment of the eyepiece (the same wheel with plus and minus signs). Basically, shooting is carried out at distances from 80 to 200 m (direct shot), and then no one will shoot on a real hunt, although the diameter of the circle, which coincides with the kill zone of a large animal, is at least 15 cm (5 MOA!). Enthusiasts of “high-precision”, varminting and some types of mountain hunting really use powerful OPs, but in the vast majority of cases, shooting is carried out from an emphasis, at serious distances, from a completely different weapon, plus arrows are not like us there. Yes, and SF-mechanics of detuning from parallax, as a rule, they have it.

On all hunting crossbows, including high-end ones, the standard sight also has modest 4x32 characteristics (see ""). Just because the distance of effective shooting is from 20 to 50 meters. In addition, if in crossbow sports the diameter of the “tens” is 4.5 mm (!), Then the kill zone of a wild boar or deer is still the same 15 cm. Well, why is the multiplicity of 9x here?

By the way, for sports crossbows (as well as rifles) - you will laugh - any optics is generally prohibited, and the good old "ring" sights are used. Imagine the level of shooting training of professional crossbowmen and bullet gunners, among which almost the majority are girls!

In general, if you are not a fan of BR and other high-precision disciplines, choose a 6x scope as a maximum. As an example - "Pilade P4x32LP", with "tactical" adjustment drums, diopter adjustment and reticle illumination.

These options are sufficient. Pancratic sights are initially more delicate, and a large magnification at any reasonable distances even for a “supermagnum” is generally not needed, except when shooting at matches (there is one). By and large, the sight in the top photo is nothing more than a “driver” known to all firefighters, successfully used in battue hunting for wild boar or deer at distances up to 150 meters.

Moreover, the letter "P" in the name indicates that the sight is also intended for spring-piston pneumatics. Which is characterized by the phenomenon of the so-called "double" (multidirectional) recoil, which is not found on any other type of weapon.


Good resistance to scrapes from budget options was also shown by Leapers sights (not long-focus lenses). For quite reasonable money these days, you can buy a device of a fairly high level (in the photo "Leapers Bug Buster IE 6X32 AO Compact").

In addition to diopter adjustment to the features of vision, there are already coated optics, multi-color stepped illumination of the “mildot” grid, a sealed nitrogen-filled housing, “tactical” correction drums and, most importantly, detuning from parallax.

In general, keep in mind that the complication of the design due to the introduction of additional options (variable magnification, detuning from parallax) worsens the survivability of most OPs in the budget segment. Really high-class optical-mechanical devices cost quite different money, for which you can buy a bag of ordinary air rifles or a couple of crossbows.

Parallax is also caused by two main mistakes when aiming:

  1. Non-optimal pupil distance from the eyepiece lens.
  2. Displacement of the pupil from the optical axis of the OP (off-center)

The first is treated by adjusting the distance when installing the sight. Simply put, move the unattached OP back and forth until the image matches the inside diameter of the telescope, with no dark area around the edges of the image.

The second is easy enough to fix through training. Train the correct tab (possible without shooting): throw the rifle into firing position and aim. And so dozens of times, every day. Until you start to set the pupil clearly in the center of the eyepiece on the machine.

A little secret that, oddly enough, not everyone knows about. Take a closer look at the behavior of stand-up shooters. They tilt their head in advance to the position it will take when aiming, and then raise the weapon, and the comb of the stock simply takes its permanent place under the cheek. At the same time, you no longer need to move your head, trying to find the correct position.

Due to the wide distribution among people close to shooting sports (a sniper is also an athlete) and hunting, a large number of various optical devices (binoculars, spotting scopes, telescopic and collimator sights), more and more questions began to arise related to the quality of the image given by such devices, as well as the factors affecting the accuracy of aiming. Since we have more and more people with education and / or having access to the Internet, the majority nevertheless heard or saw such words related to this problem as PARALLAX, ABERRATION, DISTORTION, ASTIGMATISM, etc. somewhere. So what is it and is it really that scary?

Let's start with the concept of aberration.

Any real opto-mechanical device is a degraded version of an ideal device made by man from some materials, the model of which is calculated based on simple laws of geometric optics. So in an ideal device, each POINT of the object under consideration corresponds to a certain POINT of the image. In fact, this is not so. A dot is never represented by a dot. Errors or errors in images in an optical system, caused by deviations of the beam from the direction in which it would have to go in an ideal optical system, are called aberrations.

Aberrations are different. The most common types of aberrations in optical systems are spherical aberration, coma, astigmatism, and distortion. Aberrations also include the curvature of the image field and chromatic aberration (associated with the dependence of the refractive index of the optical medium on the wavelength of light).

Here is what is written about various types of aberrations in the most general form in a textbook for technical schools (not because I cite this source because I doubt the intellectual abilities of readers, but because the material is presented here in the most accessible, concise and competent way):

"Spherical aberration - manifests itself in the mismatch of the main foci for light rays that have passed through an axisymmetric system (lens, lens, etc.) at different distances from the optical axis of the system. Due to spherical aberration, the image of a luminous point does not look like a point, but a circle with a bright The correction of spherical aberration is carried out by selecting a certain combination of positive and negative lenses that have the same aberrations, but with different signs.Spherical aberration can be corrected in a single lens using aspherical refractive surfaces (instead of a sphere, for example, the surface of a paraboloid of revolution or something something similar - E.K.).

Coma. The curvature of the surface of optical systems, in addition to spherical aberration, also causes another error - coma. Rays coming from an object point lying outside the optical axis of the system form in the image plane in two mutually perpendicular

directions, a complex asymmetric scattering spot, resembling a comma in appearance (comma, English - comma). In complex optical systems, coma is corrected in conjunction with spherical aberration by lens selection.

Astigmatism lies in the fact that the spherical surface of a light wave can be deformed during the passage of the optical system, and then the image of a point that does not lie on the main optical axis of the system is no longer a point, but two mutually perpendicular lines located on different planes at a certain distance from each other. from friend. Images of a point in sections intermediate between these planes have the form of ellipses, one of them has the shape of a circle. Astigmatism is due to the uneven curvature of the optical surface in different cross-sectional planes of the light beam incident on it. Astigmatism can be corrected by choosing lenses so that one compensates for the astigmatism of the other. Astigmatism (however, like any other aberrations) can also be possessed by the human eye.

Distortion is an aberration that manifests itself in the violation of the geometric similarity between the object and the image. It is due to the non-uniformity of the linear optical magnification in different parts of the image. Positive distortion (the increase in the center is less than at the edges) is called pincushion. Negative - barrel-shaped. The curvature of the image field lies in the fact that the image of a flat object is sharp not in a plane, but on a curved surface. If the lenses included in the system can be considered thin, and the system is corrected for astigmatism, then the image of the plane perpendicular to the optical axis of the system is a sphere of radius R, with 1/R=<СУММА ПО i произведений fini>, where fi is the focal length of the i-th lens, ni is the refractive index of its material. In a complex optical system, the curvature of the field is corrected by combining lenses with surfaces of different curvature so that the value of 1/R is zero.

Chromatic aberration is caused by the dependence of the refractive index of transparent media on the wavelength of light (light dispersion). As a result of its manifestation, the image of an object illuminated with white light becomes colored. To reduce chromatic aberration in optical systems, parts with different dispersion are used, which leads to mutual compensation of this aberration ... "(c) 1987, A.M. Morozov, I.V. Kononov, "Optical Instruments", M., VSH, 1987 .

Which of the above is important for a respected reader?

  1. Spherical aberration, coma, astigmatism and chromatic aberration can have any serious effect on the accuracy of aiming in an optical sight. But, as a rule, self-respecting firms do everything in their power to correct these aberrations as much as possible. The criterion for correcting aberrations is the resolution limit of the optical system. It is measured in angular units, and the smaller it is (at equal magnification), the better the sight is corrected for aberrations.
  2. Distortion does not affect the resolution of the sight and is manifested in some distortion of a sharply visible image. Many may have come across devices such as door peepholes and fisheye lenses, in which distortion is not specifically corrected. As a rule, distortion in optical sights is also corrected. But some presence of it in the sight, as will be said below, is sometimes very useful.

Now about the concept of parallax.

"Parallax is the apparent displacement of the observed object due to the movement of the shooter's eye in any direction; it appears as a result of a change in the angle at which this object was seen before the shooter's eye moved. As a result of the apparent displacement of the aiming pin or crosshair, an error in aiming is obtained, this parallax The error is the so-called parallax.

To avoid parallax, when aiming with a telescope, one should accustom oneself to put the eye always in the same position with respect to the eyepiece, which is achieved by a butt stock and frequent aiming exercises. Modern weapons telescopes allow moving the eye along the optical axis of the eyepiece and away from it up to 4 mm without parallax aiming error.

V.E. Markevich 1883-1956
"Hunting and sporting firearms"

It was a quote from the classic. From the point of view of a man of the middle of the century, it is absolutely correct. But time goes by... In general, in optics, parallax is a phenomenon due to the fact that the same object is observed by one observer at different angles. So the determination of the range by optical rangefinders and artillery compass is based on parallax, the stereoscopicity of human vision is also based on parallax. The parallax of optical systems is due to the difference in the diameters of the exit pupil of the device (in modern sights 5-12 mm) and the human eye (1.5-8 mm depending on the background illumination). Parallax exists in any optical device, even the most corrected for aberration. Another thing is that parallax can be compensated by artificially introducing aberration (distortion) into the optics of the ocular part of the sight so that the total distortion of the sight is zero, and the distortion of the reticle image is such that it compensates for the parallax of the sight in the entire plane of the entrance pupil. But this compensation occurs only for the image of an object located at a distance of practical infinity of the sight (the value is given in the passport). That is why some professional scopes have a so-called. parallax adjustment device (Parallax Adjust-ment Knob, Ring, etc.) rough - focus on sharpness. In non-parallax corrected scopes, it is best to actually aim with the eye directly in the center of the scope's exit pupil.

How do you know if your scope is parallax corrected or not? Very simple. It is necessary to point the center of the sight reticle at an object located at infinity, fix the sight, and, moving the eye around the entire exit pupil of the sight, observe the relative position of the image of the object and the sight reticle. If the relative position of the object and the grid does not change, then you are very lucky - the sight is corrected for parallax. People with access to laboratory optical equipment can use an optical bench and a laboratory collimator to create an infinity point of view. The rest can use a sighting machine and any small object located at a distance of more than 300 meters.

In the same simple way, you can determine the presence or absence of parallax in collimator sights. These sights have no parallax - a big plus, since the aiming speed in such models increases significantly due to the use of the entire diameter of the optics.

From the above, the conclusion is:

Dear users of optical sights! Do not bother your head with such terms as astigmatism, distortion, chromatism, aberration, coma, etc. Let this remain the lot of opticians-designers and calculators. All you need to know about your scope is whether it's parallax corrected or not. Find out by following the simple experiment described in this article.

I wish everyone a positive outcome.

Egor K.
Revision September 30, 2000
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