|Riflescopes series||Sightron SIII|
Optical products with variable magnification are more versatile as they're designed with a wider range of magnification and larger viewing angle. For example, an 8x56 rifle scope has a fixed magnification of 8x and a fixed field of view of 5 meters at 100 meters. For comparison, a rifle scope with variable magnification 3-12x56 has a more versatile magnification range for observing the whole surroundings due to the big field of view (at 3 times magnification) and in the same time a detailed evaluation of the observed object (at 12 times magnification).
With their high number of lenses in housing, optics with variable magnification are larger, heavier and have a lower permeability of light. Variable magnification is rarely present in binoculars, but it's mostly used in rifle scopes and spotting scopes. Advantages of the variable magnification regarding usability with rifle scopes and spotting scopes outweigh disadvantages – in short, one fits all. High-quality variable binoculars are very rare.
Lens diameter represents the second value in product’s name/designation. For example, 10x42 optics have 42 mm diameter of the lens at the front (those that are closer to the viewing object). It is known that the bigger the lens, the more light goes through and the image we see is brighter. All of this, however, depends on the magnification and quality of a certain optical product. Although the bigger lens diameter in binoculars is better, the size adds up on the weight, making it more heavy and difficult to handle. With riflescopes, bigger size of a lens diameter also means more problems with mounting.
The most common lens diameters are 24 mm, 42 mm, 50 mm and 56 mm.
Exit pupil is a circle from which the light is being transferred to your eye through the optical product. When you holdthe optics a bit far away from your eyes towards a light, exit pupil can be seen as a bright circle in the center of each eyepiece. The larger the exit pupil the more light can reach the eye and the image appears brighter. This is why exit pupil plays an important part in the optical products in poor light conditions at dawn or dusk. Size of the exit pupil also determines how comfortable viewing through an optical product really is. An important factor is also the size of the eye box, which is a space where the eye still has an entire picture, without any tunnel vision or blurry edges. Bigger eye box means more flexibility of the eye position and therefore more comfortable viewing, because the eye can move in several directions within the eye box and still obtain a full image.
The diameter of the exit pupil is calculated by dividing lens diameter with magnification. E. g. 8x50 binoculars have an exit pupil in the diameter of 6.25 mm.
To ensure a brighter image, the eye pupil in low light conditions has to be at least as big as the exit pupil. This way there’s no loss of light and the image is as bright as possible. However, the maximum diameter of the eye pupil depends on age. At night, children’s eye pupils can widen up to 7 mm, while with aging they decrease to a maximum of 4 mm. So if the viewer’s pupils can only be open up to 4 mm, the 7 mm exit pupil cannot be fully utilized. It may contribute to more comfortable viewing, but not to brighter image.
In daylight, when the eye pupil is open up to 3 mm, all the optics with exit pupil bigger than 3 mm are equally bright. For example, the 8x30 binoculars with 3.75 mm exit pupil are no brighter than 8x56 binoculars with 7 mm exit pupil. Those with 7 mm are however more comfortable to use, since they’re less sensitive to the eye position (they have bigger eye-box).
The only way of obtaining the whole field of view is to have the right distance between the eye and eyepiece – referred to as the eye relief. The eye relief is not necessarily a decisive factor in choosing the right optical product, however it is a useful information if you wear glasses. The eye relief then should be at least 16 mm for comfortable viewing and getting a complete image. Binoculars with too short eye relief give people with glasses a tunnel vision and only show the middle part of an image. With riflescopes the optimal distance is 90 mm or even more for safety reasons (recoil).
Without glasses the distance when using binoculars should be minimum of 15 mm, although everyone has a preferred placement as long as they’re obtaining complete field of view with no blurry edges.
Most binoculars have movable eyecups, where you can adapt them to fit different face structures (if your eyes are further away from you nose etc.) and therefore maintain a steadier grip. If you wear glasses, the eyecups should be closed down so you can lean them onto your glasses.
|Field of view
Field of view
Field of view is an area you see when looking through the optical product. Although it primarily depends on the build of the eyepiece, it is hugely affected by magnification. If you look through two binoculars of the same model but with different magnification, you can see that the one with lower magnification factor will have a wider field of view. So when comparing binoculars, you must compare the ones with the same magnification. With riflescopes the field of view is being measured at 100 m, while with binoculars, spotting scopes and other optical products it's measured at 1000 m.
With binoculars a field of view with more than 140 m at 1000 m distance is considered a wide angle, while with riflescopes it is with a field of view over 38 m at 100 m. Wide angle is particularly useful in bird-watching.
It is also important to mention that the size and lens diameter of optical products are not indicators of their field of view - bigger housing doesn’t automatically mean wider field of view.
Field of view can be expressed in two values – degrees or meters.
One degree is 17.5 m at 1000 m / 1.75 m at 100 m.
If you divide the field of view given in meters by 17.5 you get the field of view in degrees.
If you multiply degrees with 17.5 you get the field of view at 1000m.
|3 m/100 m|
In the past, twilight factor was an important value in determining the brightness of the optics. The manufacturers were using the same kind of technology and materials of the lenses therefore the optics were comparable. Nowadays, they use different types of lenses and modern coatings so the twilight factor has lost its meaning, because the brightness of the optics depends more on the quality of the coatings than on the twilight factor.
Twilight factor is calculated by the square root of multiplying magnification and lens diameter.
Twilight factor of 8x42 binoculars is a square root of 336, meaning 18.33. All the binoculars with this kind of magnification and lens diameter have the same twilight factor, but not the same brightness. If you look through an old pair of binoculars made in 1950s and a new pair with the same magnification and lens diameter you could see the difference in brightness even though they share the same twilight factor. The new pair is significantly brighter due to better lens materials and coatings.
Though manufacturers still specify the twilight factor, we recommend you to ignore it as it’s not important.
Relative brightness is a calculation of how bright the image should be when viewed through binoculars. It is presented as a square value of the exit pupil. 10x50 binoculars have an exit pupil value of 5.0 (dividing lens diameter with magnification). Square of 5.0 gives us a value of relative brightness which is 25.0. As the relative brightness value increases, we have a brighter image. On the opposite the lower the value, the darker the image.
In the past, relative brightness was an important value in determining the brightness of the optics. The manufacturers were using the same kind of technology and materials of the lenses, therefore, the optics were comparable. Nowadays, they use different types of lenses and modern coatings so the relative brightness has lost its meaning because the brightness of the optics depends more on the quality of the coatings than on the relative brightness.
Light transmission specifies an amount of light that is let through the build of optical product. Every crossing through each lens means a certain loss of light (0.1% with best coatings, up to 5% without coatings). Higher light transmission rate is very important when using optics at dawn or twilight. Good optics normally have light transmission up to 90%, whereas top-notch ones have even 95% and more light let through.
Although the quantity of light reaching the eye depends on the size of an exit pupil, light transmission determines transparency of the lenses, whether the image is dark and cloudy or bright and clear.
Light transmission can be increased with applying different coatings on the glass surfaces. However, it depends on the coating type and number of layers. Multi-layered coatings mean higher light transmission.
Uncoated glass reflects about 5% of the light (entry-level price range), single coating reduces the reflectivity to approx. 1.5% (middle price range), multi coating reduces the reflectivity to approx. 0.1 to 0.2 % (premium price range)
There are 3 options of reticle position in rifle scopes on the market:
- 1. Focal Plane (FFP)
(First) or Front Focal plane reticle position was a predominant rifle scope design in the past. Today, such reticle arrangement can only be found in tactical scopes and in a few classical European hunting scopes. The main feature of FFP reticles is their subtensions do not change with the magnification change. That means reticle subtensions in such scopes can be used for distance estimations or bullet drop compensation at any magnification setting. This is of paramount importance in tactical scenarios; thus, all real tactical scopes have FFP reticle placement. Usually, such scopes also have the clicks matched with reticle subtensions and are named MIL-MIL or MOA-MOA scopes. Another benefit of FFP reticles is the point of impact does not change with magnification change if you aim with other lines in the reticle.
The reason the majority of new hunting scopes are not produced as FFP scopes, however, is the fact these reticles are thick on highest magnification and cover more target space than SFP reticles. With super-zoom scopes with a zoom ratio of 6 times or more, this feature became even more noticeable, since FFP reticles in such scopes are thin on low magnification and thick on high magnification.
Rifle scopes with a reticle placed in their 2. (second) focal plane (SFP) are the predominant type of rifle scopes on the market. These scopes have the reticle placed in the eyepiece, at the so-called second optical focal plane. Such arrangement produces the effect that the reticle is seen the same size at all magnification settings.
Such rifle scopes are especially popular since their reticles are thin on higher magnification and offer greater precision. SFP reticles also have the advantage that, at low magnification, they are thicker compared to FFP reticles and easier to see. These two main benefits are the reason SFP rifle scopes gained such popularity.
There are, however, also some drawbacks of rifle scopes with such optical construction. Reticle subtensions change with the change of magnification, and because of that, distance calculations with the reticle are only possible at one specific magnification setting. Similarly, it is possible to use holdovers for correction of bullet drop only at one specific magnification, which makes this technique very difficult to use. The last, but minor, the drawback is that low-quality rifle scopes can have a shift of the point of impact with the magnification change.
Some rifle scopes (for example Docter Basic) have illuminated dot in the Second Focal Plane (SFP) and the reticle bars are located in First Focal Plane (FFP). This enables that on lower magnification settings the dot appears bigger on the target and the bars are thinner. Perfect for close range shots in stressful situations very common on driven hunts. However, on higher magnifications, the dot appears smaller on the target and the reticle bars thicker. This enables precise shots when aiming at greater distances. In tactical scopes, such reticle arrangement enables rapid target acquisition at 1 x magnification due to the bright and big red dot. At higher magnification reticle with hash marks can be used for holdovers.
Source: Revija Lovec
|2. focal plane - SFP|
|Adjustment per click
Adjustment per click
Adjustment per click is, how many centimeters/millimeters will move on the target at 100 m when you make one click on the turrets for elevation or a point of impact windage on the rifle scope. Clicks are usually specified in MRAD (1 mrad is 10 cm / 100 m) or MOA (1 MOA is 2.9 cm / 100 m). Some manufacturers designate MRADs with acronym MIL.
Practically all newer rifle scopes have the possibility to adjust reticle left or right (windage) and up or down (elevation). This process is known as zeroing. The upper turret on the rifle scope is for elevation adjustment of the reticle and the side turret on the rifle scope is for windage adjustment of the reticle. Hunting rifle scopes have the mechanism of both turrets protected with caps that protect the turrets from water, damage or any other outside impacts. Turrets are in other words rotatable buttons which you can spin left or right.
Every single movement made with the turret produces a »click« sound. Usually, 1 click on European rifle scopes moves hit on a target for 1 cm at 100 m range (0.1 MRAD / MIL). On American, Japanese and Chinese scopes 1 click moves the hit on the target for ¼ MOA (minute of angle) which is 7 mm at 100 m range. On Benchrest rifle scopes, where corrections have to be very small, the clicks are either 1/8 MOA (3,5 mm / 100 m) or 0,05 MRAD (5 mm / 100 m).
|7mm/100m - 1/4MOA|
Elevation is how much up and down you can adjust reticle. For example, if you see in rifle scope specifications elevation is 3.5 m, this means that you can adjust reticle maximal 1.75 m up and maximal 1.75 m down for hits on your target at 100 m. Elevation range is usually specified in MRAD (1 mrad is 10 cm / 100 m) or MOA (1 MOA is 2.9 cm / 100 m). Some manufacturers designate MRADs with an acronym MIL.
Practically all newer rifle scopes have the possibility to adjust reticle left or right (windage) and up or down (elevation). This process is known as zeroing. Upper turret on rifle scope is for elevation adjustment of reticle and side turret on rifle scope is for windage adjustment of reticle. Hunter rifle scopes has the mechanism of both turrets protected with caps which protect turret from water, damage or any other outside impacts. Turrets are easily said a rotatable buttons which you can spin in left or right way.
Every single movement made with the turret produces a »click« sound. Usually 1 click on European rifle scopes moves hit on target for 1 cm at 100 m range (0.1 MRAD / MIL). On American, Japanese and Chinese scopes 1 click moves the hit on the target for ¼ MOA (minute of angle) which is 7 mm at 100 m range.
For long range shooting elevation of at least 2.6 m / 100 m (26 MRAD or 89 MOA) is needed.
Source: Revija Lovec
|150 MOA - 5 m/100 m|
Windage is how much right and left you can adjust the reticle. For example, if you see in rifle scope specifications windage is 1.5 m / 100 m, this means that you can adjust the reticle maximal 0.75 m right and maximal 0.75 m left for hits on your target at 100 m. Windage range is usually specified in MRAD (1 mrad is 10 cm / 100 m) or MOA (1 MOA is 2.9 cm / 100 m). Some manufacturers designate MRADs with an acronym MIL.
This is a necessary function for zeroing the rifle scope since with this feature you can eliminate any misalignment with your weapon, and adjust the reticle exactly on the point of impact of your ammunition.
With windage adjustment, we can also compensate wind drift of the bullet from a straight trajectory. Wind drift is caused by the effect that a side wind has on a bullet.
Practically all newer rifle scopes have the possibility to adjust the reticle left or right (windage) and up or down (elevation). This process is known as zeroing. The upper turret on rifle scope is for elevation adjustment of reticle and side turret on rifle scope is for windage adjustment of the reticle. Hunter rifle scopes have the mechanism of both turrets protected with caps which protect turret from water, damage or any other outside impacts. Turrets are in other words rotatable buttons which you can spin in in both directions.
Every single movement made with the turret produces a »click« sound. Usually, 1 click on European rifle scopes moves hit on target for 1 cm at 100 m range (0.1 MRAD / MIL). On American, Japanese and Chinese scopes 1 click moves the hit on the target for ¼ MOA (minute of angle) which is 7 mm at 100 m range. On Benchrest of F-class rifle scopes, where the corrections have to be very small and precise, the clicks are in 1/8 MOA (3,5 mm / 100 m) or 0.05 MRAD (5 mm / 100 m).
Source: Revija Lovec
|150 MOA - 5 m/100 m|
Turrets are easily said rotatable buttons on rifle scopes which you can spin it left or right to move the reticle in the scope. This way you achieve a match of point of impact and scope reticle. This is called zeroing. The market offers different rifle scopes for different purposes and they have also different types of turrets. Determination, how will turrets look like depends on rifle scopes purpose, price, manufacturer and country of origin.
Every single movement made with the turret produces a »click« sound. Usually, 1 click on European rifle scopes moves the hit on target for 1 cm at 100 m range (0.1 MRAD / MIL). On American, Japanese and Chinese scopes 1 click moves the hit on the target for ¼ MOA (minute of angle) which is 7 mm at 100 m range.
There are 4 different types of turrets on the market
Target turrets are known as the most precise type. They are the best choice for the precise shooters, due to very small and precise adjustments. Usually they are available in 1/4 or 1/8 MOA (1 MOA = 0.29 MRAD = 2,9 cm / 100 m) or in 0,05 Mrad (1Mrad =10cm/ 100m). They are protected with caps and usually, they are very high for easier manipulation.
BDC stands for Bullet Drop Compensation. BDC turrets offer the easiest way to dial a number of clicks to compensate for bullet drop when shooting at longer distances. These turrets are usually found on hunting scopes for long-range hunting. These turrets are very similar to Tactical turrets; however, the main difference is they don’t have numbers for clicks engraved on them, but only numbers for the corresponding distances. On such turrets, 1 stands for 100m, 2 for 200m, 3 for 300m, and similar. Color dots, instead of numbers, are also very common; however, in such cases, the hunter must memorize which color corresponds to a given distance to the target.
BDC turret can only match one ballistic trajectory, and BDC turrets are always suitable for use with only one ammunition. When a shooter changes the ammunition in his rifle, the BDC turret must be changed to correspond to a new ballistic curve.
The best modern BDC turrets also have an additional function of a Zero Stop (the turret doesn’t rotate under the zeroing distance of the rifle) and locking mechanism.
Scopes meant for tactical applications have uncovered tactical turrets that offer easy control over reticle elevation and windage. Click values on such turrets are visible and a number of clicks for bullet drop compensation can be dialed fast and easy. Such turrets are especially useful in tactical situations where, usually, every target is at a different distance and not more than a couple of shots are shot at each target. Such situations demand continuously changing of reticle position in the scope elevation and windage range. Turrets covered with caps are unpractical in such situations.
Since the main purpose of tactical turrets is easy and often changing of elevation and windage position of the reticle, such turrets usually have numbers of clicks (or elevation in MOA or MRAD) clearly written on them. Resetting the turret to 0 when the rifle is zeroed is also a standard feature on such turrets. Tactical turrets are also distinguished from other types of rifle scope turrets, as the number of turns plays an important role in their usability.
Tactical turrets on basic scopes, usually, have a high number of turns from one extreme of the elevation/windage range to another. Such turrets are called multi-turn turrets. However, tactical turrets on more advanced tactical scopes have a limited number of turns. The most common are single turn – ST and double turn – DT turrets. Double turn type turrets also have an indicator, which clearly shows in which turn the turret is located. Such advanced tactical turrets are especially useful when there is no room for error when dialing a number of clicks for proper elevation adjustment.
Advanced ST and DT tactical turrets often have a Zero Stop – ZS functionality, so when a user wants to go back to turret position at which rifle is zeroed, the turret rotation is stopped at that setting.
Capped turrets are the most usual turret type on hunting scopes, where the turret covers are removed only on rare occasions when the scope is zeroed. Due to the caps, the turrets are well-protected against water, dust, and unintentional damage. On most of the hunting scopes and on some wide-angle tactical scopes, the turrets under the caps have a low height. On target scopes, this is different, since most turrets are high and easy to dial. In modern rifle scopes, turrets caps also hold the spare battery for the illumination.
Turrets on target scopes are also covered with caps; however, such scopes have much higher turrets than hunting scopes, which also have turrets covered with caps. The reason for such difference is that turrets on target/ sports scopes are dialed often when shooters shoot on different distances. However, during transportation or when shooting in the rain, high target turrets still get protected with caps.
Source: Revija Lovec
|Elevation Per Turn
Elevation Per Turn
Elevation Per Turn is when you turn a rifle scope turret for 360 degrees to the same spot where you started. For example, when you see in specifications – elevation per turn is 10 MRAD or 100 cm / 100 m, this means when you make 1 turn with turret, the point of impact on the target will be moved for 100cm on 100m range.
If elevation per turn is 24 MOA, this means that 1 turn the point of impact will be moved for 24 x 2.9 cm / 100 meters.
This information is mostly important for sport and tactical rifle scope where you often change the elevation. It’s much easier to use when the values for a turn are rounded (for example 20 MOA), but on tactical rifle scopes this mostly isn’t possible, because of big elevations, so the turrets had to be Multi-Turn (MT), what would even more complicate the use.
Source: Revija Lovec
Reticle illumination is the possibility to illuminate the rifle scope reticle with light. Some rifle scopes use reticle with illumination possibilities. There are two main types of reticle illumination on the market:
- illuminated point in the middle of the reticle,
- illumination option to light up the whole reticle.
For hunting, the reticle with central light point (dot) is more recommended. Rifle scopes that use illumination of the whole reticle are more recommended for tactical and sports use. The power of illumination light can be either day strong or visible only in the lowest light situations (in dark). For the driven hunts, IPSC or tactical CQB daytime strong illumination is more usable. Illumination option only visible in low light conditions is better for hunting in low light conditions or even in the dark. Rifle scopes that use as many different intensity levels as possible are better because they offer more possibilities to find a perfect view of the reticle in different lighting conditions.
The most advanced rifle scopes use optical fibers built in the middle of the reticle as a light dot. In high quality rifle scopes, these illuminated dots are of the smallest size. For example, if the illumination is set to OFF, you don`t see this illuminated dot at all and when you turn the illumination ON, the light dot is visible. High quality rifle scopes enable the user to fine tune illumination intensity. This way the reticle is always illuminated just right in accordance with the ambient light condition. Very dim in low light and extremely bright in the daytime. Newer rifle scopes have built in automatic turn off electronics that turns off illumination of the reticle when you don’t use your rifle scope for some time the illumination of reticle goes automatically to OFF. Such scopes have built in motion sensor to determine when the scope is not in use. This preserves battery life.
Reticle illumination option provides you a better accuracy at night and in low light situations. With non-illuminated reticles, you could have problems in low light situations, when you can see the target but not the reticle. The type of illumination for low light usage only is mostly meant for raised hide hunting.
Daytime bright illumination is the best option for driven hunting, IPSC and tactical shooting.
|Day time usable illumination
Day time usable illumination
Daytime illumination of the rifle scope reticle serves a different purpose than twilight illumination, and in such rifle scopes, high intensity levels are a necessity. The illumination of the reticle is meant for rapid target acquisition, since a bright red dot is the best possible aiming point. Shooters’ eyes are instinctively drawn to a bright red dot in the center of the field of view. Such strong illumination is feasible only in rifle scopes with magnification lower than 1.5x or ideally 1.0x. Such wide-angle rifle scopes with a real 1.0x magnification and daytime bright illumination of the reticle can even be used with both eyes open, similar to reflex/red dot sights.
Rifle scopes with daytime illumination are the best choice for IPSC, CQB, tactical shooting and driven hunting in bright daylight.
Some of the red dots and rifle scopes with reticle illumination have Auto – TurnOff function. This means, in case that you forget to turn off illumination or when you leave your firearms on table (you don’t do any movements with rifle scope), illumination automatically turns off. The time when illumination turns off is different from rifle scopes to rifles scopes.
Many of the expensive and high quality rifle scopes with illuminated reticle have an Auto-TurnOff smart motion sensor that detects different angles and automatically turns OFF or even ON the illumination of the reticle, based on the rifle scope position.
This is a nice feature to have, because this increases the battery life.
Parallax can be adjustable or fixed and parallax setting tells you if parallax is fixed, on which distance.
Adjustable parallax setting allows you to line up your reticle with your target objective in a proper plane, what brings you a proper focus, better sight image and better accuracy.
Easy explanation about parallax meaning. When your rifle with rifle scope is fixed on a bench and you are looking through the rifle scope. Your reticle is perfectly in line with the center of the target. Now you move your head around und you see also the reticle moves a little bit in relation to the target. This is parallax error. It happens when the target is not perfectly focused. When you adjust the parallax, so that the target is in perfect focus, then there is no parallax error. You can move your eye from the optical axis and the reticle will still stay in line with the center.
Traditionally, rifle scopes had a fixed parallax set at 100 meters or 100 yards; however, with the advance of shooting sports, such approach was not adequate anymore. Scopes with fixed parallax offered best resolution only at one distance (100 meters/yards) at which the target was in focus. At all other distances, the picture was less sharp or even blurry. An even bigger problem with this type of scope was the fact that, when shooting at the target not at the same distance as the scope parallax setting, the shooter had to be very careful about his eye alignment with the optical axis. If the eye is moved away from the optical axis, the reticle on the target will move, which will worsen the accuracy. Since these errors are small, the fixed parallax option is still considered accurate enough for traditional hunting. For sport shooting, though, such small error leads to poor results. Parallax errors become more pronounced with magnifications higher than 12x, and that means the majority of scopes with magnification range under this value need no parallax adjustment.
With the ability of parallax adjustment, accuracy of the riflescope is greatly enhanced at all distances. The shooter, however, has to adjust the parallax setting before making the first shot. Such scopes usually have AO – Adjustable Objective or SF – Side focus acronym in their name.
Source: Revija Lovec
Traditionally, rifle scopes had a fixed parallax set at 100 meters or 100 yards; however, with the advance of shooting sports, such approach was not adequate anymore. Scopes with fixed parallax offered the best resolution only at one distance (100 meters/yards) at which the target was in focus. At all other distances, the picture was less sharp or even blurry. An even bigger problem with this type of scopes was the fact that, when shooting at the target, not at the same distance as the scope parallax setting, the shooter had to be very careful about his eye alignment with the optical axis. If the eye is moved away from the optical axis, the reticle on the target will move, which will worsen the accuracy. Since these errors are small, the fixed parallax option is still considered accurate enough for traditional hunting. For sports shooting, though, such small error leads to poor results. Parallax errors become more pronounced with magnifications higher than 12x, and that means the majority of scopes with magnification range under this value needs no parallax adjustment.
With the ability of parallax adjustment, the accuracy of the rifle scope is greatly enhanced at all distances. The shooter, however, has to adjust the parallax setting before making the first shot. Such scopes usually have AO – Adjustable Objective or SF – Side focus acronym in their name.
With AO – Adjustable Objective scopes parallax is adjusted with a rotation of the ring on the objective bell; adjusting the parallax this way can hardly be done when in a prone position and is not the best solution for situations when parallax must be adjusted often. Due to this reason, such scopes are usually used for benchrest competitions and similar, where parallax is adjusted only initially.
With SF – Side focus scopes, parallax is adjusted with a rotation of the turret on the left side of the main tube. Such an approach offers easy adjustment of the parallax in the prone position and is the best solution for situations when parallax must be adjusted often. Due to this reason, such scopes are usually used on tactical scopes and similar, where parallax is adjusted before each shot and distances to the targets change rapidly. Scopes, which offer parallax adjustment with a side focus, are usually bigger and heavier than counterparts with parallax adjustment on Adjustable Objective. They are also more expensive to produce. Due to the size of the internal mechanism for side focus adjustment, the majority of such scopes have a tube diameter of 30mm or more.
Scopes, which offer parallax adjustment on objective bell, are usually smaller and lighter than counterparts with parallax adjustment on the side focus. They are also cheaper to make and offer adjustment that is more precise. Due to the size of internal mechanism for side focus adjustment, the majority of scopes with a tube diameter of 1 inch have an adjustable objective and not the side focus.
The easiest way to correctly set the parallax is to look at the target and gently rotate the ring on the objective. When the target is in focus and the image offers the best sharpness, move the eye from the optical axis to any direction. If the rifle is properly supported and fixed, the reticle should not move on the target when the eye is moved from the optical axis. If it does, parallax adjustment must be fine-tuned until the reticle is still, even if the eye of the shooter is moving around the optical axis.
Do not mind the meters or yards written on the adjustable objective, since they only provide an approximate value. There is nothing unusual if these values do not correspond well with the actual target distances.
Source: Revija Lovec
|Parallax adj. range
Parallax adj. Range
Parallax adj. (adjustment) range tells you the minimum and maximum distance you can adjust the parallax on your rifle scope.
Most rifle scopes (mostly) with maximum magnification 12 x have parallax setting fixed, for example, to 100m (EU 100 m / US 100 yards or 91 m). On those, you can’t make any adjustment with parallax.
Rifle scopes with more than 12 magnification zoom have adjustable parallax setting, for example, from 50m to infinity.
There are some rifle scopes with special parallax settings. Schmidt & Bender Exos rifle scopes have CC mode, which means when you turn the magnification on 1, the parallax changes simultaneously from 100 meters to 25 meters, so it is much easier to look with both eyes open and therefore easier to shoot close distance running targets.
Source: Revija Lovec
|9 m - inf.|
Diopter range in optics with one ocular (riflescopes, spotting scopes, NV optics, …)
Diopter range is an adjustment on optical products which can correct the prescription on each of your eyes. That way you can see a sharp image without wearing glasses. The diopter ring is normally located on the eyepiece and by turning it your image appears sharper.
Every optical product has different diopter range, from positive (+) to negative (-).
Diopter range in binoculars
The diopter ring is present in central focusing system on each of the barrels near the eyepiece, where you can correct the difference in the prescription of the left and right eye individually. Once you have set the right value, you can focus the image with using just the central focusing ring. If you’re wearing glasses, the diopter value should be set to 0, because the differences in your eyes are already corrected in your glasses.
To see a sharp image without wearing glasses you can easily set the diopter by looking with bare eye, turning the ring and adjusting sharpness. So when looking with both eyes your image should appear sharp. If you have astigmatism the diopter adjustment cannot correct it – you’ll still need your glasses and diopter set to 0 to see sharp images.
Optics Trade debate about Diopter settings on binoculars
|Fast focus eyepiece
Fast focus eyepiece
The eyepiece is that part of the rifle scope where you look in.
Fast focus eyepiece is a type of an eyepiece that enables fast diopter settings. With fast focus eyepiece you can adjust with rotation of the diopter setting to suite your eyes, reticle and even the target (image) at the same time.
All the newer rifle scopes have fast a focus eyepiece. There are not many rifle scopes without a fast focus eyepiece nowadays.
Older rifle scopes without fast focus had their whole eyepiece rotatable and a counter locking nut.
Optical products have many lenses in their housing. With each lens about 5% of the light passing through is lost. This can be solved with an application of coatings on the glass surfaces. With years the technology of coatings changed. At first they used only one layer, where the reduction of the loss was to 2% per surface. Today they use multiple layers of coatings where there’s minimal loss of light - 0.1% per surface. The best binoculars have even 95% of the light transmitted to the eye, through all their lenses.
With increasing transmission of the light, the coating is also important as a protectant of the optical glass and to ensure the true color fidelity, so the colors when entering are the same when exiting binoculars/riflescope. Above all, coatings also increase the image quality because all the light bouncing around on the inside can cover up detail and blur colors.
The process of applying coatings has to be precise, otherwise it can contribute to hazy and blurred image. They must be spread evenly and thinly to ensure the best quality. The better the coatings, the more expensive the optical product.
Lens coatings are as important as the quality of the lenses themselves. You can easily check whether your optical product has coatings – if you look at the reflection and it shows multiple colors such as purple, green or yellow the lenses are definitely coated. On the opposite, lenses with no coatings have a clear reflection without showing any colors.
There are many different ways of applying lens coatings:
The waterproof feature is made to keep the optical products sealed and protected from water or dust. Such products are suitable for marine, hunting, hiking or in extreme humidity. Even if you’re not planning on using them in this kind of situations, it is a good feature to have in case of heavy rain or dust. Waterproof optical products are typically sealed with O-rings.
All optical products that are fogproof are also waterproof because they have to be properly sealed to keep the dry gas inside. Yet not all waterproof products are also fogproof as the air inside the product is not necessarily replaced with dry nitrogen or argon.
You should be careful not to confuse waterproof with weather-resistant as they’re designed to protect only against light rain and are not fully sealed.
Slightly better waterproofing of binoculars can also be ensured with an individual eye focusing mechanism, due to less moving parts than with the central focusing system.
Fogging in optical products can occur when you move them from the warm insides of your house to the cold outdoors. To prevent the formation of inside fogging they’re often filled with dry gas – either nitrogen or argon which contain no moisture.
To keep the gas intact on the inside, the optics have to be properly sealed, which is why all fogproof optical products are also waterproof.
It’s important to keep in mind that fogproof means that it’s to prevent fogging on the inside of the optics, not on the outside. If your outside surface of the lenses fogs up due to temperature differences or humidity just allow them to adjust back – do not wipe the condensation off as it can be damaging to the glass surface and its coatings.
Optical products are often filled with dry gas to prevent the condensation on the inside of the housing when exposing them to temperature extremes. If there is even a slight sign of air inside, there is a certain % of moisture present. Usually they’re filled with either argon or nitrogen gas, which have the same effect – to prevent the moisture and internal fogging without affecting the optical properties. In addition, these gases also prevent the formation of fungus which would destroy the optics. Internal dewing was the biggest problem in older binoculars when exposed to lower temperatures, because they weren’t watertight and contained air. Newer binoculars are therefore all airtight and filled with dry nitrogen or argon.
Tube diameter is that diameter on the rifle scope, where mounts are clamped on (see the picture below).
Most tactical and some sport rifle scopes have the tube diameter of 34 mm, because of a thicker wall (of the tube) for a more reliable use in a harsh environment or an extended elevation range against 30 mm main tube rifle scopes.
Objective diameter is outside (housing) diameter of front side (objective) on rifle scope.
On most rifle scopes objective diameter is bigger than tube diameter. Keep in mind, the last number in the description of rifle scope tells you the size of the objective lens diameter (example: 2 – 7 x 32). Objective diameter is always bigger then lens diameter.
Objective diameter is important to know, when buying ring mounts. The bigger the objective diameter the higher mount you will need.
This information is also important for all users of clip-on devices.
Source: Revija Lovec
Eyepiece or ocular diameter is the outside (housing) diameter on the rear side of a rifle scope, directly where you look in the rifle scope itself.
The outside diameter of the eyepiece does not affect the quality of the picture, but it is an important information for users of bolt-action rifles. This dimension is important when mounting the rifle scope because you have to take into account how far your bolt handle is coming up when reloading. If the eyepiece diameter is too big, it can happen that the bolt hits the eyepiece.
The eye-piece diameter is also an important information when buying a wide-angle rifle scope and the suitable mount for it, because the eyepiece is usually bigger than the main tube, so consequently the user has to calculate the height for the mount from the eyepiece diameter and not from the objective diameter as usually.
Source: Revija Lovec
Mount length is a length of rifle scope tube where ring mounts can be clamped on (see the picture below).
Mount lengths of the tube on rifle scopes are different due to the length of objective and ocular length and sizes. Wide angle type rifle scopes have longer mount length, due to the front side of the rifle scope has a tube till the end.
Source: Optics Trade
Telescopic sights with a mounting rail under their main tube are almost always made by European producers and meant for hunting. Rail mounting brings these advantages:
- Less tensions on the scope
- More reliable mounting
- Mounting without marks on the scope
Mounting of such scopes with modern rail systems is easy and can be done by less experienced gunsmiths or even by the users. Selection of mounts is limited to premium European manufacturers, and such mounts are usually more expensive than ring alternatives.
Most common mount rail systems are:
- LM rail: a traditional prism rail under the scope. This standard was used in the past by all major European manufacturers and is commonly found on old hunting scopes. It is still used in limited production by S&B, Docter, and Kaps on their Classic lines of scopes. Mounting of scopes with LM rail is the most demanding of all rail systems since is demands drilling through the rail. Mounts made for LM rail have screws that go through the rail’s cross section.
- Zeiss ZM/VM rail: a modern standard used by the biggest number of producers. The companies that use it also call this rail standard: 45° rail, Zeiss M rail, Docter Z rail, Meopta MR rail, Minox is rail, Leica rail, or S&B LMZ. There is no drilling needed when mounting such scopes and usually 2 or 3 internal elements are inserted into the rail.
- Swarovski SR rail: the main feature of this rail system are small ribs (recoil stoppers) that prevent movements of the scope during recoil. The system is used on Swarovski and Kahles scopes, and 2 or 3 inserts in the rail are needed when mounting. All high-quality mounts made for SR rail have only one point, where small ribs are fixed, usually on the front mounting element.
- S&B Convex rail: this rail system is used exclusively by Schmidt & Bender on their hunting lines of riflescopes. The basic principle of internal parts of the rail and outer parts is the same as with Zeiss ZM/VM rail standard; however, the shape of rail is convective and not made of straight lines.
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