Comparison Gamo 3-7x20 WR vs Gamo 4X20 TVWA

The magnification provided by the scope. This parameter indicates how many times the image of any object in the field of view will be larger than that visible to the naked eye. For models with the ability to change the ratio (see below), the entire available range of adjustment is indicated.

Modern sights can be produced in a wide variety of magnifications, the only exceptions are collimators (see "Type") — they usually give a magnification of 1x, that is, in fact, do not change the visible image in any way; higher values are extremely rare and usually do not exceed 5x. In other types of sights, the maximum magnification from 2x to 5x means that this model is designed for very short distances of application. In turn, the most "far-sighted" devices can provide an increase of 17 – 20x and even more.

Note that a high magnification not only allows you to better view distant and small objects, but also narrows the field of view. With this in mind, the main criteria for choosing a sight by magnification are the expected distances of use, as well as the size and type of targets. Detailed recommendations on this matter for different situations can be found in special sources. And here we note that the degree of magnification significantly affects the cost of the sight — both in itself and due to the fact that larger (and, acco...rdingly, more expensive) lenses are desirable for "long-range" optics. At the same time, a low magnification is not necessarily a sign of a cheap device — in itself, it only means that the sight is designed for short distances and a wide field of view.

As for models with variable magnification, the wider the adjustment range — the more advanced and versatile the device is, the lower the likelihood that there is no suitable setting for a particular situation. On the other hand, expanding the range complicates the design, making it more expensive and less reliable.

The ability to change the magnification(see above) provided by the scope. This gives extended options for adjusting the device to different situations and additional convenience. So, at short distances and with large target sizes, it is more convenient to have a low magnification, and for large distances, appropriate magnifications will be required. And even at a constant distance, this adjustment can be useful: for example, for a general search for a target, it is easier to use a low magnification, which gives a wide angle of view, and upon detection, zoom in on the image for maximum aiming accuracy.

The main disadvantages of optics with this function are complexity, greater weight / dimensions and higher cost than similar models with a fixed magnification. It is also worth noting that most adjustable sights use a second focal plane, which can create some inconvenience in practical use; see "Reticle" for details.

The diameter of the exit pupil created by the optical system of the sight.

The exit pupil is called the projection of the front lens of the lens, built by the optics in the region of the eyepiece; this image can be observed in the form of a characteristic light circle, if you look into the eyepiece not close, but from a distance of 30 – 40 cm. The diameter of this circle can be calculated by dividing the lens diameter by the multiplicity (see above). For example, an 8x40 model would have a pupil diameter of 40/8=5mm. This indicator determines the overall aperture of the device and, accordingly, the image quality in low light: the larger the pupil diameter, the brighter the “picture” will be (of course, with the same lens quality, because it also affects the brightness).

In addition, it is believed that the diameter of the exit pupil should be no less than that of the pupil of the human eye — and the size of the latter can vary. So, in daylight, the pupil in the eye has a size of 2-3 mm, and in the dark — 7-8 mm in adolescents and adults, and about 5 mm in the elderly. This point should be taken into account when choosing a model for specific conditions: after all, high-aperture optics are expensive, and it hardly makes sense to overpay for a large pupil if you need a scope exclusively for daytime use.

The offset is the distance between the eyepiece lens and the exit pupil of an optical instrument (see "Exit Pupil Diameter"). Optimum image quality is achieved when the exit pupil is projected directly into the observer's eye; so from a practical point of view, offset is the distance from the eye to the eyepiece lens that provides the best visibility and does not darken the edges (vignetting). A large offset is especially important if the sight is planned to be used simultaneously with glasses — after all, in such cases it is not possible to bring the eyepiece close to the eye, and it must be at some distance from the glasses so as not to hit the glass due to recoil.

A complex indicator that describes the quality of any optical system (including sights) at dusk — when the lighting is weaker than during the day, but not yet as dim as in the deep evening or at night. It is primarily about the ability to see small details through the device.

The need to use this parameter is due to the fact that twilight is a special condition. In daylight, the visibility of small details is determined primarily by the magnification of the optics, and in night light, by the diameter of the lens (see above); at dusk, both of these indicators affect the quality. This feature takes into account the twilight factor. Its specific value is calculated as the square root of the product of the multiplicity and the diameter of the lens. For example, for an 8x40 scope, the twilight factor would be the root of 8x40=320, which is approximately 17.8. Models with adjustable magnification (see above) usually indicate the minimum twilight factor corresponding to the minimum magnification.

The lowest value of this parameter for normal visibility at dusk is considered to be 17. At the same time, it is worth noting that the twilight factor does not take into account the actual light transmission of the system — and it strongly depends on the quality of the lenses, the use of antireflection coatings (see below), etc. Therefore, the actual image quality at dusk for two models with the same twilight factor may differ markedly.

One of the parameters describing the quality of visibility through an optical device in low light conditions. Relative brightness is denoted as the diameter of the exit pupil (see above), squared; the higher this number, the more light the sight lets through. At the same time, this indicator does not take into account the quality of the lenses and their coatings used in the design. Therefore, comparing two sights in terms of relative brightness is only possible approximately, because even if the values are equal, the actual image quality may differ markedly. Also note that it makes sense to pay attention to this parameter only if the sight is planned to be used at dusk.

As for specific values, in the "dimest" models, the relative brightness does not exceed 100, in the most "bright" it can be 300 or more. Detailed recommendations regarding the choice of this parameter for certain conditions can be found in special sources. Here it is worth mentioning that the relative brightness is not directly related to the price category of the sight: models similar in this indicator can vary significantly in price.

The presence of a diopter correction function in the sight. This feature will be very useful if you wear glasses due to nearsightedness or farsightedness. By setting the required number of "plus" or "minus" diopters on the adjustment scale, you can look into the eyepiece with the naked eye and see a clear picture — the optics of the device will provide the necessary correction. This is much more convenient than watching through glasses (especially considering that due to the recoil of the weapon, it is impossible to keep the scope close to anything, whether it be the eye socket of the shooter or the glass of the glasses). However one should not forget that the correction range is usually small, and in case of serious vision failures, the capabilities of the optics may not be enough; but such situations are still quite rare.

A type of coating used in scope lenses. Anyway, we are talking about the so-called antireflection coating, which is the thinnest film (single or multilayer) on the surface of the lens in contact with air. The properties of this film are chosen in such a way as to minimize the reflection of light from the glass surface. The meaning of this function is not so much to reduce the brightness of glare that can unmask the shooter, but to increase the light transmission of the optics and, accordingly, the quality of the image visible through it.

Modern sights can be equipped with the following types of coatings:

— Illuminating. In this case, the simplest option is implied — an incomplete single-layer coating. The term "incomplete" means that not all lens surfaces are coated (although there may be several coated surfaces). Such enlightenment is inexpensive, however, the image quality is relatively low — in particular, because a single-layer film is most effective only for a part of the visible colour spectrum.

— Full illumination. Fully coated means that all surfaces of the lenses that come into contact with air have a special coating; in this case it is single layer. Such a coating is more expensive than a simple anti-reflective coating, but the quality of the “picture” when using it is higher, because. light distortion at the transitions between glass and air is minimized.

— Multi-layered illuminating. Incomplete AR coating (see above)...using multilayer films. Thanks to multiple layers, the anti-reflective coating covers the entire visible spectrum, which allows you to achieve a brighter image with less colour distortion compared to single-layer coatings; However the price of such devices is higher.

— Full multilayer enlightenment. The most advanced option: multilayer coating on all lens surfaces used in the design of the sight. Features of full and multi-layer coating are described separately above. Here we note that their combination is typical for high-class sights, because. it provides the highest quality image, but it is not cheap.

The type of aiming mark (reticle) provided in the device. There are models for which several options are indicated at once: this implies the possibility of switching between them.

As for specific varieties, in collimators, all brands have a common specificity - they should provide the convenience of quick aiming at relatively short distances. But the reticles of optical and other similar sights can be divided into hunting and tactical (sniper) sights. The former are relatively simple and have a minimum of additional elements, as they are designed for short distances and relatively large targets; and the latter are designed for high-precision shooting, military and police use, and therefore must be supplemented with various elements for measuring angles and taking corrections on the go, including between shots.

Among the specific types of grids most popular in our time are the cross with divisions, BDC, duplex, cross, half-cross, cross with a dot, cross with a circle, herringbone, rangefinder, dot, circle with a dot and circle with 2 points. Here are th...e main features of each:

— Cross with divisions. One of the most popular types of "tactical" reticles used in optical sights. The key element is the crosshair, on the lines of which additional dots are applied. The distance between the points corresponds to a strictly defined angular size; initially it was 1 MRAD (1 "mil", hence the name), however, in modern sights, other values \u200b\u200bcan be found, they should be specified according to the instructions. In addition, such grids can differ in the number of points, the presence of thickening on the lines (as in the duplexes described below), etc. Be that as it may, such a grid is very convenient for estimating distances and making corrections on the fly, many professional shooters consider it almost ideal for high-precision shooting, including at long distances, besides, the original cross with divisions (Mil-Dot) is widely used by military and police snipers around the world.
We also note that there is also a collimator variety of "mildots" - in this case, the grid looks like a circle with a dot in the middle and several dots below it, with an interval of the same 1 MRAD. However, when using collimators, the real need for making vertical corrections rarely arises, and this option is not widely used.

- Duplex. Reticles for optical and night sights (see "Type"), which look like a classic crosshair with different line thicknesses: they are thin in the center, and noticeably thicker near the edges. The meaning of this combination is that thin lines do not “clutter up” the field of view at the aiming point, and thick lines remain visible even under adverse conditions (for example, at dusk) and allow you to aim at least approximately. In addition, the thickness of large lines and the distance between their edges can correspond to well-defined angles, which allows some of these sights to be used even as simple goniometers. However, these possibilities are very limited, and in general, "duplexes" are classic hunting nets.

- Half cross. Hunting net, the main elements of which are T-shaped. One of the varieties of semi-crosses - "German grid", it is also "stump" - consists of a vertical line from the edge to the center of the sight and two horizontal lines that do not reach it; the aiming point corresponds to the upper point of the central "stump", and the thickness of the lines and the distance between them can be specified in the documentation - this allows you to carry out the simplest measurements of angles. A more modern version of the half-cross is the crosshair, in which one line (from the center to the top edge) is much thinner than the rest, or even absent altogether.

- Dot. In its pure form, the dot is used exclusively in collimator sights (see "Type"). This is an extremely convenient option for such devices: there are no unnecessary details in the field of view of the shooter, only a mark that clearly shows exactly where the weapon is aimed - more is often not required when using collimators. The disadvantages of the dot in comparison with other marks in the sights of this type include less visibility, especially in bright ambient light. However, many sights allow you to set a fairly high brightness of the mark, and sometimes even increase its size, increasing visibility. Also note that for a point, the angular size can be specified, which can be useful for quick estimation of distances.
In addition, the dot can also be used in optical and night sights, but in such cases it is usually used as an addition to another scale - for example, it additionally highlights the intersection of lines in a semi-cross.

— Circle with a dot. Another type of marks, used in collimators as the main one, and in other types of sights - as an addition to a crosshair or other more traditional grid. However, the latter is rare, so let's focus on the first option. Compared to another popular "collimator" mark - a dot - the circle covers more visible space, however, it is very noticeable and often turns out to be more convenient when shooting offhand or sharply turning the weapon to the side. In addition, for both the circle and the dot, it often indicates the exact angular size, which gives extended (compared to the usual dot) possibilities for using the aiming mark as the simplest goniometric (rangefinding) scale.

- Circle with 2 dots. A variation of the circle with a point described on top, having a second, additional point - usually below the first, at a strictly defined angular distance from it. This expands the possibilities for using the sight as an impromptu rangefinder, and also allows you to "on the move" take an amendment when shooting at long distances - just aim at the second, lower point. However, such opportunities for collimators are extremely rarely required, so this option has not received much distribution either.

- Cross. Features of this type of brand depend on the type of sights in question - optical / night or collimator (see "Type"). In classical optics, a cross is the simplest crosshair of thin lines of the same thickness. Naturally, in terms of general specialization, such reticles are hunting, but they are also found in a fairly advanced variety of sights - sports models for benchrest (shooting from a machine gun at maximum range and accuracy). The convenience of the cross in such an application lies in the fact that the lines have a minimum thickness and practically do not block the view. In nightlights, this type of grid is usually one of several options available to choose from. But in collimators, the cross is in many ways similar to a circle with a dot - it is provided as one of the large, well-marked marks with a clearly defined angular size.

- Cross with a dot. A grid in the form of a crosshair of two lines (as a rule, quite thin), at the intersection of which a clearly visible point is applied. It is in this form, as a rule, that is used in collimator and other types of sights. In the first case, such a stamp is actually a slightly modified version of the usual cross (see on top). And in optics, the presence of a point allows you to additionally highlight the crosshairs, which is convenient in some situations; the general purpose of such sights is, of course, hunting.

- A cross with a circle. Stamp in the form of a cross, complemented by a circle. It can also be used in different types of sights and has its own specialization everywhere. In classical optics, such a grid usually has a hunting purpose, although there are also varieties with additional marks that expand the "tactical" functions. And even in the absence of such marks in the characteristics, the angular size of the circle is usually specified, which provides additional opportunities for impromptu measurement of distances. We also note that the cross itself can be both ordinary and duplex (see on top). The situation is similar in night sights, however, there a cross with a circle is usually only one of the available mark options. As for the collimators, they can use both a full-fledged crosshair in a circle, and a ring with “rays” protruding from it; in any case, such a mark is more noticeable than an ordinary cross.

— BDC. This reticle got its name from the English phrase Bullet Drop Compensation, which translates as “bullet drop compensation”. The BDC ballistic reticle allows for range correction based on the bullet's trajectory. It is calibrated for a specific ammunition and sharpened for quick aiming at various distances using the same type of bullets. Distance markers in a ballistic reticle are hash marks, circles, or dots. The main sign of their placement is that the vertical markings have different gaps, increasing towards the bottom. An additional distance scale is often placed in such grids on the "six" shoulder. In addition, the ammunition for which the reticle is calibrated is usually indicated (caliber, bullet weight, weight).

- Christmas tree. Informative reticle resembling a Christmas tree in its structure. Actually, this is where the name of this type of grid came from. Each array of dots on its "six o'clock" arm is longer than the previous one - the marks increase in width when viewed from top to bottom from the central crosshair. These markers are used to correct for wind drift, which is extremely important when conducting aimed fire at long distances. The most common herringbone reticle is found in hunting hybrids, tactical sights, and military rifle scopes.

- Rangefinder. This type includes all grids that do not belong to any of the types described on top and provide for special markings for measuring angles and distances. The specific design of such markings may be different, but the general principle of operation is the same everywhere: rangefinder marks allow you to determine the angular size of a visible object, and if the linear size of this object is known, you can easily estimate the distance to it (at least approximately). Each type of rangefinder reticle has its own rules for use.