Parallax - what is it? Parallax and aberrations of optical sights Is parallax detuning necessary?

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

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

Conclusion . Parallax is absent 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 reticle are in the same plane.

The effect of parallax in the scope depends on two main factors:

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

The optical systems of sights differ depending on whether this device is with a fixed or variable magnification, whether the 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). There are two planes that play a role in parallax: the imaging plane and the reticle focusing plane. A target at a distance of 1000 meters 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 focus plane of the reticle. Naturally, we are talking about very small shifts, such as 0.1mm, which, of course, seems to be very scanty, but in fact this value is aggravated (considered as a product with magnification) by increasing the device. Each magnification of the scope increases the parallax error. For example, let's say you've got the best parallax alignment but made a 0.1mm error in the alignment (alignment) of the image plane relative to the focal plane of the reticle. This error will change with the adjustment of the magnification of the instrument. For the sake of simplicity, let's say our scope has a magnification range of 1x to 20x (which would be super cool!). So, initially the parallax was tuned for 1x as good as possible, but still an error of 0.1mm was made. By rotating the zoom ring and setting it to the 20x position, the alignment error was equivalently increased by a factor of 20. Those. now the alignment 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 (impossible). In fact, parallax is inherent in all scopes. However, it is believed that there is a certain distance at which parallax is absent. 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 are other factors affecting the parallax effect. So, for example, the optical imperfections of the lens can also lead to parallax. Spherical aberration, astigmatism, not properly corrected by the manufacturer, will result in image formation at a significant distance from the grid. No parallax detuning will save you from defects in the optical system. In addition, if the reticle is not accurately (precisely) positioned in the scope barrel at a certain distance from the objective, the result will be an exaggeration of the non-parallax distance. 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 parallax phenomenon is not a significant problem for a normal deer hunter, and even if the scope is equipped with a parallax detuning mechanism, you can leave it off, 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 tuning (tuning, fine-tuning) is required for better parallax correction.

Parallax adjustment is an absolute must for those who use very high magnifications, shoot with the same scope at very different ranges, or shoot at very close or very long distances. In such cases, the sight must be equipped with a parallax adjustment mechanism, since even small errors in aiming (aiming) will subsequently lead to a significant loss in 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, low magnification scopes, such as chasing scopes, can also do without parallax detuning, since at low magnification the parallax effect is quite small and unimportant for fast (fast target) aiming accuracy, so it can be neglected in practice.

There is a fairly common mistake when the parallax detuning 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 (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 operation. And this is completely wrong. The focusing ring on the eyepiece should be used only to focus on the grid, it is best to focus the grid while looking at the sky or a white sheet of paper, this will avoid the misunderstanding of trying to focus on distant objects instead of the grid. In fact, it is enough for the shooter to adjust the focus on the reticle once, achieving its maximum sharpness, adjusting the diopter correction ring (focusing ring on the eyepiece) to the individual characteristics of vision, and this is enough. This should be done in advance, because the human eye has a natural ability to adapt and focus on the image, which in turn will lead to a misalignment of the scope.

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

There are the following parallax adjustment methods:

• rear focus(Second Focal Plane Type Correction) or parallax adjustment on the eyepiece. In this method, a ring is located directly in front of the eyepiece with a scale from the minimum distance (usually 50 yards) to the maximum distance (usually infinity). The ring looks exactly like the zoom ring in variable power scopes, but in this case it is responsible for parallax detuning. This method is quite rare, usually only in fixed magnification scopes above 8x and below 20x magnification. 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 handwheels for entering horizontal and vertical corrections. The marking of distances is located along the perimeter of the drum. The flywheel is conveniently positioned for left-handed rotation without looking up from sighting through the scope.

• 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 scope's lens with distance markings applied to it. A fairly common parallax adjustment method.

• fixed parallax or fixed (factory) parallax adjustment. Sights with factory parallax adjustment do not provide for self-adjustment, there are no additional mechanical components for adjustment. These scopes are factory set for parallax for a specific range, typically 100 yards, 150 yards, or 200 yards. By the way, the good news is that, as a rule, in scopes up to 7x magnification, the parallax will be no more than 2 inches at a distance of 400 yards.

Each shooter is faced with the problem of choosing which parallax system to buy a scope with. And there is no single right or wrong decision. It is likely that an avid shooter will have more than one sight in his arsenal, and, of course, they may differ in both 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 it may be preferable to have a sight with a fixed parallax, for others - with detuning on the lens or side detuning. However, it is worth noting that scopes with side detuning are somewhat more expensive, and scopes with detuning on the lens can suffer from the phenomenon of floating MTP (mid point of aim). Therefore, when buying a sight with parallax detuning, carefully study its behavior at different settings.

We wish you good shooting and good accuracy!

Knowing the distance between observation points D ( base) and offset angle α in radians, you can determine the distance to the object:

For small angles:

The reflection of the lantern in the water is significantly shifted relative to the almost unshifted sun

Astronomy

Daily parallax

Daily parallax (geocentric parallax) - the difference in directions to the same luminary from the Earth's center of mass (geocentric direction) and from a given point on the Earth's surface (topocentric direction).

Due to the rotation of the Earth around its axis, the position of the observer changes cyclically. For an observer located at the equator, the parallax base is equal to the radius of the Earth and is 6371 km.

Parallax in photography

Viewfinder Parallax

Viewfinder parallax is the discrepancy between the image seen in the optical non-mirror viewfinder and the image obtained in the photograph. Parallax is almost imperceptible when photographing distant objects, and quite significant when photographing close objects. It arises due to the presence of a distance (basis) between the optical axes of the lens and the viewfinder. The parallax value is determined by the formula:

where is the distance (basis) between the optical axes of the lens and the viewfinder; - focal length of the camera lens; - distance to the aiming plane (object).

Viewfinder parallax (scope)

A special case is the parallax of the sight. Parallax is not the height of the sight axis above the barrel axis, but the error in the distance between the shooter and the target.

Optical parallax

Rangefinder Parallax

Rangefinder parallax - the angle at which an object is seen during focusing with an optical rangefinder.

stereoscopic parallax

Stereoscopic parallax is the angle at which an object is viewed with both eyes or when photographed with a stereoscopic camera.

Temporal parallax

Temporal parallax is a distortion of the shape of an object by parallax that occurs when shooting with a camera with a curtain shutter. Since the exposure does not occur simultaneously over the entire area of ​​the photosensitive element, but sequentially as the slit moves, then when shooting fast moving objects, their shape may be distorted. For example, if an object moves in the same direction as the shutter slit, its image will be stretched, and if it moves in the opposite direction, then it will be narrowed.

Story

Galileo Galilei suggested that if the Earth revolved around the Sun, then this could be seen from the variability of parallax for distant stars.

The first successful attempts to observe the annual parallax of stars were made by V. Ya. Struve for the star Vega (α Lyra), the results were published in 1837. However, scientifically reliable measurements of the annual parallax were first carried out by F. W. Bessel in 1838 for the star 61 Cygnus. The priority of discovering the annual parallax of stars is recognized by Bessel.

see also

Literature

• Yashtold-Govorko V.A. Photography and processing. Shooting, formulas, terms, recipes. Ed. 4th, abbr. - M.: "Art", 1977.

Links

• The ABC's of Distances - An overview about measuring distances to astronomical objects.

Wikimedia Foundation. 2010 .

See what "Parallax" is in other dictionaries:

- (astro) the angle formed by visual lines directed at the same object from two differences. points. As soon as the parallax of the object and the distance between the two points from which this object was observed are known, then the distance of the object from ... ... Dictionary of foreign words of the Russian language

- (from Greek parallaxis deviation) 1) a visible change in the position of an object (body) due to the movement of the observer's eye. 2) In astronomy, a visible change in the position of a celestial body due to the movement of the observer. Distinguish between parallax, ... ... Big Encyclopedic Dictionary

parallax- apparent displacement of the object under consideration when changing the angle of its perception or moving the observation point. Dictionary of practical psychologist. Moscow: AST, Harvest. S. Yu. Golovin. 1998. parallax ... Great Psychological Encyclopedia

PARALLAX, the angular distance that a celestial object appears to be displaced relative to more distant objects when viewed from opposite ends of the base. Used to measure the distance to an object. Star parallax... ... Scientific and technical encyclopedic dictionary

PARALLAX, parallax, husband. (Greek parallaxis evasion) (astro). The angle that measures the apparent displacement of the luminary when the observer moves from one point in space to another. Daily parallax (the angle between the directions to the luminary from a given place ... Explanatory Dictionary of Ushakov

- (from the Greek parallaxis deviation) the apparent displacement of the object in question when the angle of its perception changes ... Psychological Dictionary

- (from the Greek parallaxis deviation) in aviation, astronautics, the lateral displacement of the plane of the final orbit of the aircraft relative to the starting point, usually measured along a great circle arc from the starting point of the aircraft to the track ... ... Encyclopedia of technology

- (from the Greek. parallaxis deviation) in astronomy, a change in the direction of the observer astro. object when the observation point is shifted equal to the angle under the eye from the center of the object, the distance between the two positions of the observation point is visible. Usually used P., ... ... Physical Encyclopedia

Exist., Number of synonyms: 1 offset (44) ASIS Synonym Dictionary. V.N. Trishin. 2013 ... Synonym dictionary

parallax- Apparent change in the position of an object in relation to another object when the viewpoint changes... Geography Dictionary

Parallax is the apparent movement of the target relative to the reticle as you move your head up and down when you look through 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. This is the definition of parallax from a shooting point of view, where most shots are fired at distances over 100 meters and the depth of field (DOF) is large.

Shooting airguns is another matter. When using a high magnification scope at relatively close range (up to 75 meters), the image will be out of focus (blurred) 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 wish to shoot.

A few years ago it was discovered that the side effect of parallax/focus correction was that if the scope had sufficient magnification (greater than 24x) it could be used for typical airgun ranges, with a shallow depth of field this 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 "correction / adjustment of parallax", field target received an elementary, but very accurate rangefinder.

Parallax Adjustment Types

There are 3 types: front (lens), side and back. Back - focus is adjusted using a ring close in size and location to the zoom ring (zoom - approx.transl.). Rear focusing scopes are rare and none have found their way into field targeting to date, so they will not be considered further. What remains is front focus and side focus.

I) Adjustable lens (front focus)

It is relatively simple mechanically and generally less expensive than a side focusing mechanism. There are expensive exceptions such as the Leupold, Burris, Bausch&Lomb and these models are popular in field targets due to their exceptional optical qualities. However, there is an ergonomic disadvantage to using parallax on the lens and this is due to the fact that you have to reach for 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". The Leupold line of scopes includes scopes where the lens does not rotate; the lens only moves when you use the knurled ring. In most front focus scopes, the entire front lens housing rotates.

It can be very difficult to rotate smoothly and may result in distance measurement becoming secondary as the scope was not designed with this feature in mind. Consequently, these are simpler sights that do not contain too many optical elements, so the possibility of possible errors and malfunctions is very low.

There are various tricks to make distance reading easier, such as some kind of collar around the lens or a prism to view the scale from the shooting position. The left-handed shooter may find this type of scope more comfortable than sidewheel scopes.

II) Side focus

Side-wheel scopes in field targeting 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 marks on the wheel can be read without acrobatic exercises, i.e. violation of the position.

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

Side wheel scopes are usually only supplied with a handle that is too small to accommodate the 1 yard and 5 yard scale steps needed for the field target. This little wheel works for its intended purpose - as a parallax correction device, not as a rangefinder.

Instead, a large wheel is installed on top of the existing one. Larger wheels are usually made of aluminum and are held in place with threaded studs or screws. The 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 turn out that it is necessary to make a pointer on the wheel in order to replace the stock one. A thin piece of plastic or metal sandwiched between the upper and lower half rings and placed along the edge of the wheel should be sufficient.

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

Calibrating "parallax adjustment" as a rangefinder

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

You must have access to the 50m line, roulette and targets. It is especially important that you use the correct type of target to set up your course markings. Standard falling FT targets are the best because they will be your only source of information for estimating 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 black for the kill zone.

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

It may be necessary to wrap a piece of tape around the parallax adjustment wheel to provide a surface on which to write numbers. Pointed permanent markers are the best option for tape recording. Alternatively, sticker numbers can be used to mark directly on polished aluminium. Now is the time to decide which labeling method you will use.

It is an unfortunate 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" side wheel is about 25mm. Between 50 and 55 yards this decreases to about 5mm. Consequently, long ranges are the most difficult to determine and repeat. The 20 yard mark is a good place to start. This is above the scope's lower focus limit, but not far enough to be difficult.

Place both targets at 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. Do the following:

1. Focus your eye on the reticle first. Turn the wheel until the target is approximately in focus.
2. Repeat, but try to decrease the amount of wheel movement until the target image is clear and sharp.
3. Using stationery, make a tiny (!) mark on the wheel next to the "pointer".
4. By repeating steps 2 and 3, you are looking for marks that will be in the same place each time you take a measurement. If so, you can mark it with a number and make it your permanent value for that distance. If it turns out to be impossible and you still get some marks, you can simply compromise between the extreme marks or take as the operating point the place where they are the most dense and label the value.
5. Repeat steps 1-4 with the white target. The marks may be in the same place, but they may not be. Record the difference when going from black to white target. It is important to practice the rangefinder in various lighting conditions. This is important because the human eye will accommodate much faster if the image is highly detailed and fairly simple. As the wheel spins, your brain tries to correct the image from blurry to sharp a bit before it gets REALLY sharp. This difference depends on the lighting conditions, your age, current physical condition, etc. You can reduce this effect by always spinning the wheel at the same speed, not too fast, but not "millimeter by millimeter". The image will focus more definitely if you make larger movements, like 5-10 yards and not just 1-2 yards.

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

That's why you should focus your eyes first on the crosshairs of the reticle and just take a little look at the target or just use your peripheral vision to observe the target while keeping while focusing on the crosshairs. In this way, the target will be seen sharply while the reticle also remains sharp (Figure 3).

Fig.1	Fig.2	Fig.3

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

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

Most scopes used in the FT cannot measure distances from 8 yards, only from 10 or 15 yards. If you turn the zoom down, you will see these close targets more sharply, but never really clearly. A "focus adapter" can help 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 in the manner described earlier. Now you have a sight that will work as a rangefinder for all distances of the marked trajectory.

Now for the test. Need a friend or colleague. Ask them to set up several targets at various distances, each of which has been measured with a tape measure. They will have to record these distances. Then measure the distance to each of the targets, in turn telling the value of each to your friend. It will write the named values ​​next to the measured distances.

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

* * * * * * * * * * * * * * * * * * * * * * * * *

If you have followed this guide up to this point, you have set up your rifle and scope 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, more or less every scope suffers from it. The main reason for this is the change in temperature, but also on the height above sea level. Or some light filters may affect it. If we want to compare the behavior of different sights due to rangefinder errors, it is always recommended to consider a rangefinding error of 55 yards at 10 degrees of temperature difference. This value was 0.5-4 yards on the scopes I tested.

There are several different ways to deal with parallax shift, from appropriate scale shift and slanted distance marks to multiple (or adjustable) pointers. But the point is that you have to recognize your scope and its rangefinder at different temperatures.

Unfortunately, there is only one way to find out about the necessary corrections: you have to test the sight at different times of the year and time of day, placing targets every 5 yards and measuring them many times, very accurately. It is important that the riflescope remain in the shade and be 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 can be continuous with temperature changes, but it can't be "almost nothing and then all of a sudden a 'jump'". If you already know how your scope works, you will also know how much and how to compensate to get correct range results.

Isolating the scope is completely useless because it can only protect from direct sunlight, but it is still exposed to ambient heat and parallax shift will occur. Also, water cooling is not a good idea :-) We can do two things that are really useful: monitoring the ambient temperature, or even better if the scope itself (see picture below). And, of course, keep your sight in the shadows at all times. The shot only takes 2-3 minutes so the scope can't get too much heat and has 10-15 minutes to get back to air temperature.

BFTA Riflescope Mounting Instructions
- Updated Maestro

In motion, parallax means a change in the location of an object against some background relative to an observer who is in place. This term has gained popularity on the Internet. In particular, the site looks interesting, in the design of which there are dynamic elements. Parallax is a web page design technique used by webmasters to attract large numbers of visitors.

What is parallax

Parallax scrolling can be used vertically as well as in a straight line. Nintendo is the best example. Many of us remember with nostalgia computer games, represented by the movement of the main characters from the left side of the screen to the right. It is also possible to move down, carried out along a vertically located straight line. often used on the web. To create a vertical slider, you can use JavaScript or CSS 3.

For them, the described three-dimensional spatial effect is just characteristic. The creators of the games used several background layers. They differ in texture, while the movement is carried out at different speeds.

Do not think that parallax is only a possibility to create a 3D effect. On the page, you can move the existing icons. Moreover, it looks quite attractive. A particularly good option is to use an individual trajectory for each of them. In this case, different icons are used, moving along different trajectories. Such a design attracts attention.

Animated picture

It's hard to find a site without images. High-quality and demonstrative drawings attract visitors. But the most attention is drawn to various kinds of dynamic images. Indeed, if there is movement when visiting a site, then this attracts attention. Significantly increases the likelihood of a visitor returning to a resource to a dynamic image. Did it seem to move or not? Therefore, to attract visitors to the site, it is worth exploring such a thing as the parallax effect.

Examples of websites with moving images:

• hvorostovsky.com;
• www.kagisointeractive.com

As shown in the examples, the experience is improved by drop-down menus into sub-items. Such an element saves time for visitors, therefore it is attractive to them.

jQuery Library

The term jQueryParallax defines the library of the same name. Thanks to it, it is easy to achieve the effect of movement in 3D format. In the jQuery library, 3D perception is created in a variety of ways. One of them consists in the horizontal simultaneous movement of background objects at different speeds. This library is characterized by the presence of a large number of different kinds of properties. And the displacement described here is only a small part of its capabilities.

The site looks quite attractive, for the creation of which various modern elements were used. One of them is parallax. Example sites might look like this:

• www.grabandgo.pt
• www.fishy.com.br
• www.noleath.com
• buysellwebsite.com.

jParallax is represented by layers that move with the mouse. Dynamic elements tend to have an absolute ;). Each of them is characterized by its own size and movement at an individual speed. It can be text or an image (at the request of the creators of the resource).

Site visitor perception

After that, a person usually pays attention to the fact that the page is designed with high quality, conveniently and competently. This fact is usually respected. It happens that curiosity arises to try other elements. There are a huge number of identical sites on the Internet. How to make your resource special?

If you like the design, the visitor will stay for a longer period. Thus, the likelihood that he will be attracted by the posted information increases, he will show interest. As a result, a person will use the offered service, product or promotional offer.

Favorite old games

The concept of "parallax" should be familiar to all fans of consoles from the 80s and 90s. This applies to games:

1. Mario Bros.
2. Mortal Kombat.
3. Streets of Rage.
4. moon patrol.
5. Turtles in Time.

That is, parallax is a technique that has been used for a sufficiently long period. These games are really remembered with some nostalgia. After all, they seem to be imbued with the character of that period.

The images on the screen are created using a technique such as parallax scrolling. There is nothing surprising in the fact that this technique has gained well-deserved popularity. This design concept is quite warmly perceived by those who played in the 80-90s or watched the leisure of friends.

Parallax scrolling

Marketers of the world's leading brands have long used all sorts of technical advances. Thus, it becomes possible to interest even a casual visitor to the site.

Parallax scrolling has been used quite successfully by Nike. The company's original website was designed by Weiden and Kennedy. But this design did not survive. The resource was gradually updated, in accordance with the trends of our time. Activatedrinks.com is an example of a site whose design is reminiscent of the one used by the Nike marketers of this period.

There shouldn't be too many speakers.

Do not forget that the design of the site is often the key criterion that guides the visitor. A poorly executed resource usually leaves the user with the impression that the owner company is not serious. But a site with all sorts of attractive design elements indicates the desire of the owners of the organization to interest visitors.

Here it is worth remembering about parallax. This is a wonderful tool. But even they shouldn't get too carried away. Because the page, on which there are a large number of various kinds of moving elements, is quite difficult to perceive. It is best to make the design moderately stylish and understandable.

Individual elements that need to be highlighted should be dynamic. There may also be a picture that is created using layers moving one relative to the other. Do not forget that the user site is designed primarily for visitors. It does not have to be a masterpiece of a webmaster who has put all his knowledge into it. After all, such an approach will only complicate perception.

How to create a site navigation

How to make parallax? This question is of interest to many website builders. It is not necessary to know the intricacies of writing tags. It is very convenient to use special resources on the Internet. From the large number of proposals available, the following assistants can be distinguished:

1. Plax is a program that is fairly easy to use. It tends to give the page mobility due to the movement of the mouse.
2. jQuery Parallax Image Slider - A jQuery plugin used to create image sliders.
3. Jquery Image Parallax - suitable for designing transparent drawings. Through its use of PNGs, GIFs take on depth, animated by movement.
4. Curtain.js is used to create a page with fixed panels. In this case, the effect of opening the curtains is observed.
5. Scrolling Parallax: A jQuery Plugin is to create a parallax effect when scrolling the mouse wheel.

Some more useful plugins

As you know, information has the greatest value. And the greater the number of ways to achieve the desired is known, the closer the probability of obtaining the correct result. Useful plugins used to create dynamics:

1. jQuery Scroll Path - used to place objects on the specified path.
2. Scrollorama is a jQuery plugin. It is used as a tool for attractive material design. Allows you to “revive” the text on the page due to convenient scrolling.
3. Scrolldeck is a jQuery plugin. It is a great solution used as a presentation for sites designed as one page.
4. jParallax represents the movement of layers depending on the movement of the mouse pointer.
5. Stellar.js is a plugin with which any element is designed with the addition of a parallax scrolling effect.

Parallax anchored to cursor

Such a parallax looks quite impressive. At first glance, the objects of the site page, which are stationary at first glance, move when approached. It seems to come to life and follows the element being moved.

First, stop at the picture. The required image is placed in a frame, while its edges must be hidden. The method is very simple, and the resulting picture looks quite attractive.

The parallax effect for the site is a wonderful way to design. Its use indicates that due attention was paid to the creation of the resource. Therefore, it is worth paying attention to the services offered or information to read. Such sites look more advantageous against the background of identical, but simply designed resources.

Space is one of the most mysterious concepts in the world. If you look at the sky at night, you can see a myriad of stars. Yes, probably, each of us has heard that there are more stars in the Universe than grains of sand in the Sahara. And scientists from ancient times have been drawn to the night sky, trying to unravel the mysteries hidden behind this black void. Since ancient times, they have been improving methods for measuring cosmic distances and the properties of stellar matter (temperature, density, rotation speed). In this article, we will talk about what stellar parallax is and how it is used in astronomy and astrophysics.

The phenomenon of parallax is closely related to geometry, but before considering the geometric laws underlying this phenomenon, let's plunge into the history of astronomy and figure out who and when discovered this property of the movement of stars and was the first to put it into practice.

Story

Parallax as a phenomenon of changing the position of stars depending on the position of the observer has been known for a very long time. Even Galileo Galilei wrote about this in the distant Middle Ages. He only assumed that if a change in parallax for distant stars could be seen, this would be evidence that the Earth revolves around the Sun, and not vice versa. And it was absolutely true. However, Galileo could not prove this because of the insufficient sensitivity of the then equipment.

Closer to our days, in 1837, Vasily Yakovlevich Struve conducted a series of experiments to measure the annual parallax for the star Vega, which is part of the constellation Lyra. Later, these measurements were recognized as unreliable when, in the year following Struve's publication, 1838, Friedrich Wilhelm Bessel measured the annual parallax for the star 61 Cygnus. Therefore, no matter how sad it may be, the priority of discovering the annual parallax still belongs to Bessel.

Today, parallax is used as the main method for measuring distances to stars and, with sufficiently accurate measuring equipment, gives results with minimal error.

We should move on to geometry before looking directly at what the parallax method is. And to begin with, let's recall the very basics of this interesting, albeit unloved by many, science.

Fundamentals of Geometry

So, what we need to know from geometry to understand the phenomenon of parallax is how the values ​​of the angles between the sides of a triangle and their lengths are related.

Let's start by imagining a triangle. It has three connecting lines and three angles. And for each different triangle - their angles and lengths of the sides. You cannot change the size of one or two sides of a triangle with the same values ​​of the angles between them, this is one of the fundamental truths of geometry.

Imagine that we are faced with the task of finding out the value of the lengths of two sides, if we know only the length of the base and the values ​​of the angles adjacent to it. This is possible with the help of one mathematical formula that relates the values ​​of the lengths of the sides and the values ​​of the angles lying opposite them. So, let's imagine that we have three vertices (you can take a pencil and draw them) that form a triangle: A, B, C. They form three sides: AB, BC, CA. Opposite each of them lies an angle: angle BCA opposite AB, angle BAC opposite BC, angle ABC opposite CA.

The formula that links all these six quantities together looks like this:

AB / sin(BCA) = BC / sin(BAC) = CA / sin(ABC).

As we can see, everything is not quite simple. From somewhere we have a sine of angles. But how do we find this sine? We will talk about this below.

Fundamentals of trigonometry

The sine is a trigonometric function that determines the Y-coordinate of an angle built on the coordinate plane. To show this clearly, they usually draw a coordinate plane with two axes - OX and OY - and mark points 1 and -1 on each of them. These points are located at the same distance from the center of the plane, so a circle can be drawn through them. So, we got the so-called unit circle. Now let's build some segment with the origin at the origin and end at some point on our circle. The end of the segment, which lies on the circle, has certain coordinates on the axes OX and OY. And the values ​​of these coordinates will represent the cosine and sine, respectively.

We figured out what a sine is and how to find it. But in fact, this method is purely graphical and was created rather to understand the very essence of what trigonometric functions are. It can be effective for angles that do not have infinite rational values ​​of cosine and sine. For the latter, another method is more effective, which is based on the use of derivatives and binomial calculation. It is called the Taylor series. We will not consider this method because it is quite complicated to calculate in the mind. After all, fast computing is a job for computers that are built for it. The Taylor series is used in calculators to calculate many functions, including sine, cosine, logarithm, and so on.

All this is quite interesting and addictive, but it's time for us to move on and return to where we left off: on the task of calculating the values ​​of the unknown sides of a triangle.

Sides of a triangle

So, back to our problem: we know two angles and the side of the triangle to which these angles are adjacent. We only need to know one corner and two sides. Finding the angle seems to be the easiest: after all, the sum of all three angles of a triangle is 180 degrees, which means that you can easily find the third angle by subtracting the values ​​of two known angles from 180 degrees. And knowing the values ​​​​of all three angles and one of the sides, you can find the lengths of the other two sides. You can test this yourself with any of the triangles.

And now let's finally talk about parallax as a way to measure the distance between stars.

Parallax

This, as we have already found out, is one of the simplest and most effective methods for measuring interstellar distances. Parallax is based on the position of a star depending on its distance. For example, by measuring the angle of the apparent position of a star at one point of the orbit, and then at its directly opposite point, we get a triangle in which the length of one side (the distance between opposite points of the orbit) and two angles are known. From here we can find the two remaining sides, each of which is equal to the distance from the star to our planet at different points in its orbit. This is the method by which the parallax of stars can be calculated. And not only stars. Parallax, the effect of which is actually very simple, despite this, is used in many of its variations in completely different areas.

In the following sections, we will take a closer look at the applications of parallax.

Space

We have talked about this more than once, because parallax is an exceptional invention of astronomers, designed to measure the distances to stars and other space objects. However, not everything is so clear-cut here. After all, parallax is a method that has its own variations. For example, there are daily, annual and secular parallaxes. One can guess that they all differ in the time interval that passes between the measurement stages. It cannot be said that an increase in the time interval increases the measurement accuracy, because each type of this method has its own goals, and the measurement accuracy depends only on the sensitivity of the equipment and the selected distance.

Daily parallax

Daily parallax, the distance with which is determined using the angle between the straight lines going to the star from two different points: the center of the Earth and a selected point on the Earth. Since we know the radius of our planet, it will not be difficult, using the angular parallax, to calculate the distance to the star using the mathematical method we described earlier. The main use of diurnal parallax is to measure nearby objects such as planets, dwarf planets, or asteroids. For larger ones use the following method.

annual parallax

Annual parallax is still the same method of measuring distances, with the only difference that it focuses on measuring the distances to stars. This is exactly the case of parallax that we considered in the example above. Parallax, the determination of the distance to a star by which can be quite accurate, must have one important feature: the distance from which the parallax is measured must be the greater the better. The annual parallax satisfies this condition: after all, the distance between the extreme points of the orbit is quite large.

Parallax, examples of methods of which we have considered, is certainly an important part of astronomy and serves as an indispensable tool in measuring the distances to stars. But in reality, today they use only a yearly parallax, since the daily parallax can be replaced by more advanced and faster echolocation.

Photo

Perhaps the most famous type of photographic parallax is binocular parallax. You must have noticed it yourself. If you bring your finger to your eyes and close each eye in turn, you will notice that the angle of view of the object changes. The same thing happens when shooting close objects. Through the lens, we see the image from one angle of view, but in fact the photo will come out from a slightly different angle, since there is a difference in the distance between the lens and the viewfinder (the hole through which we look to take a photo).

Before we end this article, a few words about why such a phenomenon as optical parallax can be useful, and why it is worth learning more about it.

Why is it interesting?

For starters, parallax is a unique physical phenomenon that allows us to easily learn a lot about the world around us and even about what is hundreds of light years away: after all, using this phenomenon, you can also calculate the size of stars.

As we have already seen, parallax is not such a distant phenomenon from us, it surrounds us everywhere, and with the help of it we see as it is. This is certainly interesting and exciting, and that is why it is worth paying attention to the parallax method, if only out of curiosity. Knowledge is never redundant.

Conclusion

So, we have analyzed what the essence of parallax is, why it is not necessary to have complex equipment to determine the distance to the stars, but only a telescope and knowledge of geometry, how it is used in our body and why it can be so important for us in everyday life. We hope the information provided was useful to you!