Parallax adjustment with option. Parallax adjustment in optical sights

Parallax is visible movement target relative to the reticle as you move your head up and down while looking through the scope's eyepiece. This occurs when the target is not hit on the same plane as the reticle. To eliminate parallax, some scopes have an adjustable lens or a 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, the scope is at its maximum magnification, the scope is said to be free of parallax. This is the definition of parallax from a firearms point of view, where most shots are fired at distances of more than 100 meters and the depth of field (depth of field) is large.

Shooting with air guns is a different matter. When using a scope with significant magnification at relatively close range (up to 75 meters), the image will be out of focus (blurry) in any range other than the one it is currently set to. This means that in order to have an acceptable picture, the "objective" or side focus must be adjusted for each of the distances you want to shoot at.

Several years ago it was discovered that side effect Parallax/focus correction was such that if the scope had sufficient magnification (greater than 24x) it could be used for typical airgun ranges, and at shallow depth of field it made accurate distance estimation possible. By marking the parallax adjustment wheel at the distances at which the image was in focus, which has now become a simple “parallax correction/adjustment,” the Field Target received a basic but very accurate rangefinder.

Types of Parallax Adjustment

There are 3 types: front (lens), side and rear. Rear - focus is adjusted using a ring close in size and location to the zoom ring. Rear-focus sights are rare and none have found their way into field target applications to date, so they will not be discussed further. What remains is front focus and side focus.

I) Adjustable lens (front focus)

This is a relatively simple mechanical focusing mechanism and usually less expensive than a side focusing mechanism. There are expensive exceptions, such as Leupold, Burris, Bausch & Lomb, and these models are popular among field targets due to their exceptional optical qualities. However, there is an ergonomic disadvantage to using parallax on the lens and this comes from having to reach to the front of the scope to adjust it while aiming.

This is a particular problem in standing and kneeling shooting. Some models, such as the Burris Signature, have a “resettable calibration ring.” Leupold's line of scopes includes scopes where the lens does not rotate; the lens only moves when you use the knurled ring. On most front-focus scopes, the entire front lens housing rotates.

This can be very difficult to rotate smoothly and may result in the distance measurement becoming secondary since the scope was not designed with such a function in mind. Consequently, these are simpler sights that do not contain too many optical elements, so the likelihood of possible errors and malfunctions is very low.

There are various tricks to make reading distances easier, such as some type of clamp around the lens or a prism to view the scale from the shooting position. A left-handed shooter may find this type of sights more comfortable than side-wheel sights.

II) Side focus

Side wheel sights in field target sights are now the norm rather than the exception. Although usually expensive and limited in range, they offer one big advantage over front parallax models: ease of access to the side wheel instead of the front of the scope. The distance markings on the wheel can be read without acrobatic exercises, that is, violation of the position.

The side wheels are generally easier to turn than the lens, hence more precise adjustments are possible. However, this mechanism is much more vulnerable. If a wheel has play, you should always measure in the same direction to compensate for the play.

Side wheel sights typically only come with a handle, which is too small to accommodate the 1-yard and 5-yard scale increments required for a field target. This small wheel works for its intended purpose - as a parallax correction device, and not as a rangefinder.

Instead, a large wheel is installed on top of the existing one. Larger wheels are typically made of aluminum and are held in place with grub screws or grub screws. Original handles are usually 20-30 mm in diameter. "Custom" wheels typically range in size from 3 to 6 inches in diameter.

It may also be necessary to have a wheel indicator made to replace the stock one. A thin piece of plastic or metal sandwiched between the top and bottom half rings and positioned along the edge of the wheel should be sufficient.

You can see some really huge wheels around the world, but they shouldn't be bigger than 6-7 inches as it's more vulnerable and the resolution won't improve. you will have big step scale, but the errors will be larger too. It is advisable to mount the reticle on the scope itself (for example, using a third mounting ring, or using an existing pointer on the scope), rather than mounting something between the two rings of the scope mount. So you don't have to calibrate the parallax again unless you have a reason to remove the scope.

Calibrating “parallax adjustment” as a rangefinder

This is the most difficult part of the entire scope operation procedure. In the process, you may become frustrated and tired, and prolonged eye strain can cause wasted time and effort. During competition, everything you do during the shooting process will be wasted if you don't mark the correct distance, so being careful with your parallax marking is sure to pay dividends.

You must have access to the 50 meter line, tape measure and targets. It is especially important that you use the correct type of target to set up your range markings. Standard falling FT targets are best because they will be your only source of information for judging distances during competition. Take two of these targets and spray paint one of them black and white - the kill zone. Paint the second one white and the kill zone black.

Place the targets at a safe distance and shoot about ten times at each. This will provide a contrast between the paint on the target and the gray metal of the target itself. Using the nylon cord, tie several large knots through the metal ring on the front panel. Separate loops and windings on the cord can be invaluable in solving the problem of accurate focusing.

It may be necessary to wrap a piece of tape around the parallax wheel to provide a surface on which to write the numbers. Pointed permanent markers are the best option for writing on tape. You can also use sticker numbers to apply markings directly to polished aluminum. Now is the time to decide which marking method you will use.

It's a sad fact that the greater the distance, the smaller the pitch between the marks, merging into one after 75 yards. The average distance between 20 and 25 yards on a 5-inch side wheel is about 25mm. Between 50 and 55 yards this decreases to about 5mm. Consequently, long ranges are the most difficult to detect and repeat. The 20 yard mark is good place for starters. This is above the lower limit of the scope's focus, but not so far as to be difficult.

Place both targets exactly 20 yards from the front lens of the sight. It is important that the front lens is used as the reference point for all your measurements, otherwise it may result in inaccurate distance readings. Follow these steps:

1. Focus your eye first on the reticle. Rotate the wheel until the target is approximately in focus.
2. Repeat, but try to reduce the amplitude of the wheel action until the target image is clear and sharp.
3. Using stationery, make a tiny (!) mark on the wheel next to the “pointer”.
4. Repeating steps 2 and 3, you look for marks that will be in the same place every time after taking a measurement. If so, you can mark it with a number and make it your constant value for that distance. If this turns out to be impossible and you do end up with multiple marks, you can simply compromise between the extreme marks or take as the operating point where they are densest and write the value.
5. Repeat steps 1-4 with the white target. The marks may end up in the same place, but they may not. Record the difference when moving from a black to a white target. It is important to practice rangefinder in different conditions lighting. This is important because the human eye adapts much faster if the image is highly detailed and simple enough. As you spin the wheel, your brain tries to correct the image a little from blurry to sharp before it gets REALLY sharp. This difference depends on lighting conditions, your age, physical fitness V at the moment etc. You can reduce this effect by always turning the wheel at the same speed, not too fast, but not “millimeter by millimeter.” The image will focus more clearly if you make larger movements, such as 5-10 yards and not just 1-2 yards.

As noted earlier, it is important not to try too hard. As soon as you concentrate on the target, your own eyes will try to compensate for parallax errors and focus the target while the crosshairs are out of focus (Figure 1). You won't notice this until you stop looking at the target, at which point you notice that the crosshairs are sharp and the target is suddenly blurry and out of focus (Figure 2).

This is why you should focus your eyes first on the reticle and just take a small glance at the target or just use your peripheral vision to observe the target while maintaining while the main focus is on the crosshairs. This way, the target will be seen sharply while the reticle also remains sharp (Fig. 3).

Fig.1	Fig.2	Fig.3

With the 20-yard parallax adjustment complete, move 5 yards further. Repeat this procedure for every 5 yards from 20 to 55 yards, constantly checking with other distances to make sure nothing has changed. If things start to change, take a break and try again.

Once the 20-50 yards have been completed, set the short distances to the accuracy of your choice. As noted earlier, setting 17.5 yards for the 15 to 20 range and then a 1 yard step down from 15 yards should be more than enough. When you reach the close range range of your scope, check with a tape measure. You may only have to move the target six inches to determine this distance. It might end up being 8.5 yards or something like that.

Most scopes used in FT can't measure beyond 8 yards, only 10 or 15 yards. If you turn the zoom all the way down, you'll see those close targets more sharply, but never really clearly. A "focus adapter" can help with this problem, but many shooters can live with it anyway. Regardless of the distance, set the elevation for that distance by shooting at one of the cardboard targets using the technique described earlier. Now you have a sight that will work as a rangefinder for all distances of the marked trajectory.

Now for the test. You will need a friend or colleague. Ask them to set up several targets at different distances, each measured with a tape measure. They will have to record these distances. Then measure the distance to each of the goals, in turn telling the value of each to your friend. He will write the named quantities next to the measured distances.

This interesting exercise, because it checks your data in real life. At a pre-measured distance, your brain can deceive you because you know how far away the target is. The test simulates competition conditions because you have absolutely no way to know for sure the distance to the target other than your scope. There is a saying in field target and it is very true: Trust Your Scope - Trust Your Scope.

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If you have followed this guide up to this point, you have your rifle and scope set up and are capable of winning any competition. The rest, as they say, is up to you. Welcome to Field Target. Enjoy!

Parallax shift

Parallax shift is a well-known phenomenon, and more or less every scope suffers from it. The main reason for this is the change in temperature, but also from the altitude. Or some filters may affect it. If we want to compare the rangefinder error behavior of different scopes, it is always recommended to consider the rangefinder error at 55 yards at a 10 degree temperature difference. This value was 0.5-4 yards for the scopes I tested.

There are several different ways to combat parallax shift, from appropriately shifting the scale and slanted distance markers to multiple (or adjustable) pointers. But the point is that you have to get to know your scope and its rangefinder at different temperatures.

Unfortunately, there is only one way to find out about the necessary fixes: you must test the scope in different times year and time of day, placing targets every 5 yards and measuring them many times, very accurately. It is important that the scope remains in the shade and outdoors for at least half an hour before taking measurements.

After a dozen experiments, you will see how your scope reacts to temperature. The parallax shift may be continuous as the temperature changes, but there cannot be "almost nothing and then suddenly a 'jump'." If you already know how your scope works, you will also know how much and how to compensate to get correct ranging results.

Isolating the scope is completely useless because it can only protect against direct sun rays, but it is still subject to heat from environment and a parallax shift will occur. Besides, water cooling is not a good idea :-) We can do two things that are really useful: monitoring the temperature of the environment or better yet the scope itself (see picture below). And, of course, keep your sights in the shadows all the time. The shot only takes 2-3 minutes, so the scope can't get too much heat and has 10-15 minutes to return to air temperature.

Instructions for Installing the BFTA Sight
- Updated Maestro

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

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

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

Parallax displacements 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 away from the center 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 of the star. It is easy to understand from Fig. 2 that the annual parallax can also be defined as the angle at which the semimajor axis of the earth’s orbit, located perpendicular to the line of sight, is visible from the star.

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

For those closest to you celestial bodies- The Sun, Moon, planets, comets and other bodies of the Solar System - 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, parallax is calculated for an imaginary observer moving from the center of the Earth to the equator point at which the star is on the horizon. To determine the distance to the star, calculate the angle at which the equatorial radius of the Earth is visible from the star, perpendicular to the line of sight. This parallax is called daily horizontal equatorial parallax or simply daily 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 displacement (the so-called trigonometric parallaxes) only for the nearest stars located no further than several hundred parsecs.

However, the study of stars for which trigonometric parallaxes have been measured has revealed a statistical relationship between the type of spectrum of a star (its spectral class) and absolute magnitude (see “Spectrum-luminosity” diagram). Having extended this dependence also to stars for which the trigonometric parallax is unknown, they were able to estimate the absolute magnitudes of the stars by the type of spectrum, and then, comparing them with visible magnitudes, astronomers began to estimate the distances to the 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 - using variable stars of the Cepheid type (this method is described in the article Cepheids); such parallaxes are sometimes called Cepheid parallaxes.

Speaking of sights, parallax phenomenon can be defined as a visible change in the position of an object in the field of view relative to the aiming reticle. So, if the (primary) image of the observed target formed by the lens is in front of or behind the aiming reticle, and not in the same plane, then the result is the phenomenon of parallax. Parallax also appears when the eye is shifted from the optical axis of the sight.

You can check whether they are in the same or different planes by simply moving your eye left and right or up and down. If parallax is present, the reticle will appear to move relative to the target.

Conclusion . There is no parallax if the shooter's eye is located exactly on the optical axis of the sight, or if the primary image of the object and the aiming reticle are in the same plane.

The parallax effect in a scope depends on two main factors:

• The distance at which the object is removed relative to the objective lens of the device.
• How far the shooter's eye is displaced relative to the optical axis of the sight, which is determined by the size of the exit pupil.

Optical systems of sights differ depending on whether the device has a fixed or variable magnification, whether the aiming reticle is located in the first focal plane ( FFP) or in the second focal plane ( SFP) (read in detail Optical sights with a reticle in the first or second focal plane). For parallax, two planes play a role: the imaging plane and the reticle focusing plane. A target 1000 meters away will be in focus at a specific point behind the objective lens. A target at a distance of 100 meters will come into focus at a different point, further from the objective lens compared to the focus of a 1000 meter target.

Parallax adjustment allows you to align the target image with the reticle focusing plane. Naturally we're talking about about very small movements, such as 0.1mm, which, of course, seems very insignificant, but in fact this value is aggravated (considered as a product with an increase) by increasing the device. Each time the scope is magnified, the parallax error increases. For example, let's say you adjusted the parallax in the best possible way, but made an error in alignment (adjustment) of the image plane relative to the focal plane of the grid by 0.1 mm. This error will change as the magnification of the device is adjusted. For the sake of simplicity, let's assume that our scope allows for magnification ranging from 1x to 20x (which would be super cool!). So, initially the parallax was adjusted for 1x as well as possible, but still there was an error of 0.1mm. By rotating the zoom ring and setting it to the 20x position, the adjustment error was equivalently increased by 20 times. Those. Now the adjustment error is as much as 2mm! And this is already a lot for the optical system of the sight and its planes!

The parallax effect will be absent at any distance as long as the shooter's eye is on the optical axis of the sight. To completely eliminate parallax, a very small exit pupil is required, which is practically impossible (not feasible). In fact, parallax is inherent in all scopes. However, it is believed that there is a certain distance at which there is no parallax. In most scopes, this zero parallax point is usually located at the corresponding point in the middle of the scope's focal range.

It is worth noting that there is also other factors affecting the parallax effect. For example, optical imperfections in the lens can also lead to parallax. Spherical aberration and astigmatism not properly corrected by the manufacturer will lead to the formation of an image at a significant distance from the grid. No amount of parallax adjustment will save you from defects in the optical system. Additionally, if the reticle is not precisely positioned in the scope barrel at a certain distance from the lens, the resulting no-parallax distance will be exaggerated. Unreliable fixation (mounting) of the reticle, leading to displacements of only thousandths of a millimeter, will subsequently lead to a changing parallax value.

Of course, the phenomenon of parallax is not a significant problem for the average deer hunter, and even if the scope has a parallax adjustment mechanism, you can not use it, set it to 100m and then simply ignore it. Do not forget that the marking (scale) of the distances of the parallax adjustment mechanism is not absolutely accurate, it is an approximate, general rough (approximate) estimate; fine adjustment (tuning, fine-tuning) is required for better parallax correction.

Parallax adjustment is an urgent need for those who use very high magnifications, shoots with the same sight at distances that are strikingly different from each other, or those who shoot at very close or very long distances. In such cases, the sight must be equipped with a mechanism for adjusting parallax, since even small errors in aiming (aiming) will subsequently lead to a significant loss of shooting accuracy. By adjusting the lens assembly in the instrument's optical system, the target can be “moved” exactly to the focal plane of the reticle for any distance.

By the way, tactical sights often do not have parallax adjustment, since you can never predict the exact distance to the target. In addition, scopes with low magnification, in particular driven scopes, can also do without parallax adjustment, since at low magnification the parallax effect is quite small and is of little importance for fast target aiming accuracy, so it can be neglected in practice.

A fairly common mistake that occurs is when the parallax adjustment mechanism is used to focus the reticle. For this purpose it is necessary to use focusing ring on the eyepiece device. This is actually the only purpose of this node. Often shooters do the opposite: they try to use the reticle focusing mechanism (the ring on the eyepiece) to focus the image, and the parallax adjustment mechanism to focus the reticle, which naturally causes dissatisfaction with the quality of the device and its performance. And this is completely wrong. The focusing ring on the eyepiece should be used only to focus on a reticle, and it is best to focus the reticle while looking at the sky or a white piece of paper, this will avoid the misunderstanding of trying to focus the image on distant objects instead of the reticle. In fact, the shooter only needs to adjust the focus on the reticle once, achieving its maximum sharpness by adjusting the diopter correction ring (focusing ring on the eyepiece) to individual characteristics sight, and that's enough. This should be done in advance, as the human eye has a natural ability to adapt and focus on the image, which in turn will lead to an error in sight adjustment.

Let us once again pay attention to the fact that, as practice shows, the markings on the parallax adjustment mechanism are relative. The given graduation is most likely just a guide, a reference point, but does not eliminate parallax at the selected magnifications and settings. In fact, the only way to get better results and get it right after the diopter adjustment ring has been adjusted correctly is to slowly rotate the parallax adjustment mechanism until the target is sharp and clear and until you are sure that that slight deviations of the eye from the optical axis of the sight do not lead to a displacement of the aiming reticle relative to the target.

The following are distinguished: parallax adjustment methods:

• Rear Focus(Second Focal Plane Type Corection) or parallax adjustment on the eyepiece. In this method, there is a ring located directly in front of the eyepiece with a scale from the minimum distance (usually 50 yards) to the maximum (usually infinity). The ring looks exactly like the zoom ring in scopes with variable magnification, but in this case it is responsible for parallax adjustment. This method is quite rare, usually only in scopes with a fixed magnification, the magnification of which is above 8x and below 20x. Parallax adjustment on the eyepiece is implemented in such sights as, for example, the SWFA SS 10x42 tactical sight or the Sightron SIII 10X42 MMD sight.

• Side Focus(SF) or side parallax adjustment. As a rule, the parallax adjustment drum is located on the left next to the flywheels for entering horizontal and vertical corrections. Distance markings are located around the perimeter of the drum. The flywheel is conveniently positioned to rotate with your left hand while still observing through the sight.

• Adjustable Objective(AO, Front Objective Lens Type Correction) or parallax adjustment on the lens. This method allows you to make adjustments by rotating the ring on the sight lens with distance markings printed on it. A fairly common method for adjusting parallax.

• Fixed Parallax or fixed (factory) parallax adjustment. Sights with factory parallax adjustment do not provide for independent adjustment; there are no additional mechanical components for adjustment. These scopes are factory parallax adjusted for a specific range, typically 100 yards, 150 yards, or 200 yards. By the way, good news and that, as a rule, scopes with magnification up to 7x will have no more than 2 inches of parallax at 400 yards.

Every shooter is faced with the problem of choosing which parallax adjustment system to buy a scope with. And there is no single right or wrong decision here. It is likely that an avid shooter will have more than one scope in his arsenal, and, naturally, they may differ in magnification, lens diameter, and parallax adjustment method. Depending on the type of shooting, distance and a number of other individual selection criteria, for some tasks a sight with fixed parallax, for others - with detuning on the lens or side detuning. However, it is worth noting that scopes with side adjustment are somewhat more expensive, and scopes with lens adjustment may suffer from a phenomenon called floating MPO (mid-point of aim). Therefore, when purchasing a scope with parallax adjustment, carefully study its behavior at different settings.

We wish you accurate shooting and good accuracy!

Parallax - a phenomenon detected when observing the surrounding space, which consists in a visible change in the position of some fixed objects relative to others located at different distances from each other, when the observer’s eye moves. We encounter the phenomenon of parallax at every step. For example, looking out of the window of a moving train, we notice that the landscape seems to rotate around a distant center in the direction reverse movement trains. Near objects move out of the field of view faster than distant objects, which is why the landscape appears to be rotating. If objects lie in the same plane, then parallax will disappear, there will be no different movements of objects relative to each other when the eye moves.

Parallax in sights is the discrepancy between the plane of the target image formed by the lens and the plane of the sighting reticle. Tilting the reticle causes parallax at the edges of the field of view. This is called oblique parallax. The lack of a flat target image in the sight over the entire field of view, due to poor-quality manufacturing of the lenses and sight assembly, or due to significant aberrations of the optical system, causes “irremovable parallax.” Typically, a sight is made in such a way that the image of a target 100-200 m distant is projected by the lens into the plane where the aiming reticle is located. In this case, the parallax range seems to be halved between distant and near targets. As the target approaches the shooter, its image also moves closer to the shooter (in an optical system, the target and its image move in the same direction). Thus, in the general case, a sight is characterized by a mismatch between the target image and the reticle. When the eye moves perpendicular to the axis of the sight, the target image moves in most cases in the same direction relative to the center of the reticle. The target seems to “move” away from the aiming point; when tilting or shaking the head, it “darts” around the aiming point. In addition, the reticle and the target are not clearly visible at the same time, which worsens the comfort of aiming and minimizes the main advantage of a telescopic sight over a conventional one. Because of this, a sight without focusing on the shooting distance (without a parallax elimination device) allows for a highly accurate shot only at one specific distance. A high-quality scope with a magnification greater than 4x must have a device to eliminate parallax. Without this, it is quite difficult to find and keep the eye in in the right position, on the line connecting the reticle and the point on the target, the reticle is generally not in the center of the field of view. A slight movement of the reticle along with the target image can be detected when shaking the head, especially when the eye moves away from the calculated position of the exit pupil, which is explained by the presence of distortion in the sight eyepiece. This can only be eliminated in scopes that have a parabolic lens in the eyepiece. Focusing a sight is the operation of setting the image produced by the lens in a given plane - the plane of the aiming reticle. The relationship between the longitudinal shift of the focusing lens and the amount of image displacement is determined by calculation. Typically, scopes either move the entire lens or an internal component located near the reticle. A scale indicating the focusing distance in meters is applied to the lens frame of the sight. By moving the lens to the desired division (firing distance), you eliminate parallax. A sight containing a focusing device is, of course, a more high-quality and complex product, since the moving lens must maintain its position in space relative to its own axis, that is, keep the line of sight unchanged. This centering of the lens focusing component relative to the geometric axis of the lens tube is achieved by maintaining tight manufacturing tolerances of the focusing component.

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 along the entire exit pupil of the sight, observe the relative position of the object image and the sight reticle. If the relative position of the object and the reticle 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 infinitely distant point of view. The rest can use a sighting machine and any small object located at a distance of more than 300 meters. The same in a simple way you can determine the presence or absence of parallax in red dot sights. The absence of parallax in these sights is a big plus, since the aiming speed in such models increases significantly due to the use of the entire diameter of the optics.

Due to its wide spread among people close to shooting sports (a sniper is also an athlete) and hunting, large quantity various optical instruments (binoculars, spotting scopes, telescopic and collimator sights) questions increasingly began to arise related to the quality of the image provided by such devices, as well as about the factors affecting the accuracy of aiming.

Let's start with the concept aberrations. Any real optical-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 geometric optics. Thus, in an ideal device, each point of the object under consideration corresponds to a certain point in the image. In fact, this is not so. A point 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 go in an ideal optical system, are called aberrations. There are different types of aberrations. Most common the following types aberrations of optical systems: 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).

Spherical aberration - manifests itself in the mismatch of the main foci for light rays passing through an axisymmetric system (lens, objective, 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 core and a halo weakening towards the periphery. 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 similar).

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 a complex asymmetric scattering spot in the image plane in two mutually perpendicular directions, resembling a comma in appearance (comma, English - comma). In complex optical systems, coma is corrected together with spherical aberration by selecting lenses.

Astigmatism lies in the fact that the spherical surface of a light wave can be deformed when passing through an 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 some distance from each other 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 caused by the uneven curvature of the optical surface in different cross-sectional planes of the light beam incident on it. Astigmatism can be corrected by selecting lenses so that one compensates for the astigmatism of the other. Astigmatism (as well as any other aberrations) can also occur in the human eye.

Distortion is an aberration that manifests itself in a violation of the geometric similarity between the object and the image. It is due to the uneven linear optical magnification in different areas of the image. Positive distortion (the increase in the center is less than at the edges) is called pincushion distortion. Negative - barrel-shaped.
The curvature of the image field is that the image of a flat object is sharp not in the 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, and 1/R=, where fi- focal length of the i-th lens, ni is the refractive index of its material. In a complex optical system, field curvature is corrected by combining lenses with surfaces of different curvatures so that the value of 1/R is zero. Chromatic aberration is due to the dependence of the refractive index transparent media on the wavelength of light (light dispersion). As a result of its manifestation, the image of an object illuminated by 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

In “experienced” conversations, 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 in the target image relative to the reticle image when the eye moves away from the center of the eyepiece. This is due to the fact that the target image is not focused exactly in the focal plane of the reticle.
Maximum parallax occurs when the eye reaches the end of the scope's exit pupil. But even in this case, a scope with a constant 4x magnification, adjusted for parallax at 150 m (at the factory), will give an error of about 20 mm at a distance of 500 m.
On short distances The parallax effect has virtually no effect on the accuracy of the shot. So, for the scope 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 you keep your eye centered on the eyepiece (on the optical axis of the scope), the parallax effect is practically absent and does not affect shooting accuracy in most hunting situations.

Sights with factory parallax adjustment

Any sight with a fixed lens focusing system can be adjusted against parallax only at one specific distance. Most scopes have a factory parallax adjustment of 100-150 m.
The exceptions are low magnification sights, oriented for use with a shotgun or combined weapon (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 further than the distance the sight is factory adjusted for parallax. Example: "tactical" sight The KAHLES ZF 95 10x42 is factory parallax adjusted to 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 influenced by a lot of factors related, first of all, 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 values ​​significantly exceeding the deviation caused by parallax when firing from a rifle clamped in a vice in an absolute vacuum.
Another criterion: parallax does not appear significantly until the magnification factor exceeds 12x. Another thing is scopes for target shooting and varmint, like, say, 6-24x44 or 8-40x56.

Sights 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 body of the central tube and a corresponding distance scale. This focusing system allows you to combine the target image and the image of the aiming mark in the same focal plane.
To eliminate parallax at a selected distance, you must do the following:
1. The image of the aiming mark must be clear. This must be achieved using your scope's focusing mechanism (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 distance value opposite the corresponding mark.
3. Securely secure the weapon in the most stable position and look through the scope, concentrating on the center of the reticle. Raise your head slightly and then lower your head. The center of the aiming mark must be absolutely motionless in relation to the target. Otherwise, perform additional focusing by rotating the ring or drum until the movement of the mark center is completely eliminated.
The advantage of sights with parallax adjustment on the body of the central tube or on the eyepiece is that when adjusting the sight, the shooter does not need to change position when preparing to shoot.

Instead of output

Nothing happens for nothing. 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 arises to think about additional settings in 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 (USA) and (Austria).

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The company "World Hunting Technologies" is the official representative in the Russian Federation of optical sights of the brands Kahles, NightForce, Leapers, Schmidt&Bender, Nikon, AKAH, Docter. But in our assortment you can also find sights from other famous manufacturers. All scopes sold by us come with a full manufacturer's warranty.

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

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