What you need to know about reflex sights  

What are reflex sights, what can they do and why they can be an inexpensive alternative to other optics. We explain all of that here.
Absehen und Ziel „werden“ zu einer optischen Ebene
The reticle and target become one optical level.

What exactly is a red dot sight?

A red dot sight (also known as a luminous dot, collimator or reflex sight) is an opto-electronic aiming aid for long and short weapons. It no longer has three levels (rear sight, front sight and target); now only two levels (luminous dot and target) must lie on an optical axis. The luminous point is also perceived intuitively rather than specifically, so that one does not concentrate on it when aiming and thus the two levels "red point and target" blur into one level "red point on target". Reflex sights do not emit an active, visible beam; in contrast to classic rifle scopes, they rarely or never work with magnification, but instead are parallax-free. They are designed for dynamic targeting and also allow sighting with both eyes open. The eye distance is irrelevant and the typical center sighting, as with a rifle scope, is no longer necessary. They are suitable for both the Close Quarter Battle (CQB, battle in a confined space) and for short to medium operational distances of 100–150 meters.

The classic areas of application include, for example, driven hunting, shotgun hunting and dynamic shooting disciplines over short to medium distances (up to 150 meters with targets at various distances from the shooter), and trap or skeet shooting at 15-25 meters. For the 15 meter range, the Mini reflex sights with the 32MOA ring (e.g. the HS507C or HE508T-RD), are particularly suitable because at a distance of 15 meters it corresponds approximately to the diameter of the target.

How does a reflex sight work?

The basic technical principle of red dot sights is easy to explain: basically, a small LED creates a colored point of light that is reflected against a small, spherical, semi-transparent mirror and thrown back onto the front lens as a luminous target. Since the semi-transparent mirror only reflects a percentage of the light, it enables a correspondingly sharp view through the lens. The shooter can see both the target and the reflected point in one image line through the special mirror. Since the light beam of the point appears precisely from the direction of the sighting line, the point always appears in the right place, regardless of the position of the eye relative to the sighting device.

Nevertheless, you should know the point of impact of your weapon at different distances. Similar to a rifle scope, the point of impact can be corrected by adjusting the reticle. 

The red dot is generated using a beam splitter.

The red dot is generated with the help of a curved, semi-transparent mirror.

The red dot is generated with the aid of a curved, semi-transparent mirror.

Differences between reflex sights - open or closed?

The differences between open and closed reflex sights are obvious. Open models also mean open to outside influences: the light source of the open model is located in a (partly) open constructed housing. Dirt, snow or rain can cloud, falsify or fog the light source, impairing the display of the illuminated dot. Closed sights have the light source within an encapsulated housing and are therefore not susceptible to such influences. These models can therefore be used in almost all weather conditions without any problems.
Offen konstruiertes Reflexvisier
Open design reflex sight HS510C
Geschlossen konstruiertes Reflexvisier
Closed design reflex sight HE512T-RD

Differences between reflex sights - laser or light emitting diode point?

Many ask: Why is this point so razor-sharp? Very simple: Models with a straight front lens generate the luminous point using a laser, which is split into various small points using a prism and thus shaped into a point. However, many small points are required for this, which is why the illuminated point can sometimes appear blurred. In addition, the prism lens is expensive, so such devices also cost more money.

In other models with a beveled front lens, the point is generated by an LED and a semiconductor mirror. The shape of the (circular) point is already specified and can be represented much more sharply with the aid of the light-emitting diode. You don't need a prism (read: no expensive lens) for this, but one that is beveled and projects the point into the image plane. That is why these models are cheaper, but not less qualitative. To the contrary. 

How do you use a reflex sight correctly?

With reflex sights the answer is: "With two eyes open". It all sounds simple, but what happens very intuitively for some users becomes a real problem for others. Especially those who have been using a rifle scope for years or right-handed people who have a left-dominant eye have to get used to this change. To get used to a reflex sight, you can train with a covered or taped exit lens, for example. As a shooter, you initially only perceive the outside environment and the red dot in front of a dark background. After a while you get used to the perception and can clear the front lens again.

Anvisierung mit beidseitig geöffneten Augen
Sighting with eyes open on both sides.

The history of reflex sights

The idea of a reflex sight was born in 1900. The telescope manufacturer, Howard Grubb, registered his invention for a patent (No. 12108), after which it was first used in the military (Air Force) in 1918. In the Second World War it was used in various artillery and anti-tank weapons. Unfortunately, there was a lack of small, powerful lighting elements, which is why passive light sources were needed. It wasn't until the mid-1970s that the Swedish company Aimpoint achieved the decisive breakthrough: the developers were able to use the bundled light beam of an LED as a light source for the reflex sight. This technology also made it possible to build much smaller reflex sights and thus also made it possible to use them on handguns.

The advantages of reflex sights

Reflex sights are - depending on the model - small, light and quite handy. They are ideal for quick sighting over short and medium distances, as both eyes can be open, and, depending on the distance (for example in combination with a magnifier), form a noticeably inexpensive alternative to classic rifle scopes.

As already mentioned above, the biggest advantage over a classic open sight is that it makes target acquisition easier: the rear sight, front sight and target no longer have to be brought into one optical axis; with the reflex sight only the luminous point and target have to match, and with reflex sights they lie in one plane. When using reflex sights with both eyes open, the so-called tunnel vision, which one is used to with telescopic sights, is eliminated and both spatial and peripheral vision are completely preserved. Thus target acquisition can be accelerated enormously by catching most, if not all, aiming errors such as tilting.

Ein ARD (Killflash) kann Lichtreflexe verhindern
An ARD (Killflash) can prevent light reflections.

Disadvantages of reflex sights

The biggest disadvantage of the reflex sights is the luminosity of the red dot at night. Depending on the brightness setting, it may overlap the target. For this reason, you should pay attention to sufficient day and night vision levels for brightness control.

Reflex sights can fog up in the event of sharp temperature fluctuations or condensed breath. Openly constructed models in particular are very susceptible to moisture, rain or dirt. So if you want to aim under extreme conditions, you do much better with closed reflex sights (container designs).

Another disadvantage, which does not only affect reflex sights, is the possible reflection of sunlight through the front lens. To prevent this, you should use a honeycomb Killflash / ARD (Anti Reflection Device), which you can usually mount in front of the lens as an attachment.

Although short to medium range use can be a great advantage of reflex sights, it can be a disadvantage for some who like to shoot over longer distances. If you don't want to part with your reflex sight despite the distance, you can always mount a magnifier with optical magnification and diopter adjustment in front of it.

What should you consider when buying a reflex sight: 

Before buying a reflex sight, every shooter should know what performance he or she expects for the given price. There are countless suppliers with an unmanageable number of models and features, so you should always think about what the sight should be able to do before buying. In general, it is always advisable to look at prices, equipment and (if possible) place of manufacture. Visier magazine writes the following:  

 “Models manufactured in Germany or in the USA already have a higher production cost. Japanese manufacturers, on the other hand, are professionals when it comes to the quality of optical lenses and electronics, and deliver both at comparatively lower costs.”

When making a purchase decision, the point size, point sharpness and point color should be important factors: point reticle only or switchable to circle/circle dot ? Do you prefer green reticle color or gold due to the weakness in red-green vision? You should ask yourself these questions beforehand. Most manufacturers indicate the size of their luminous dots in MOA (minute of angle, about 2,8 cm at 100 meters or 1 inch at 100 yards). For long guns and shooting distances of up to 150 meters, point sizes of <3 MOA are recommended, for short weapons <4MOA. 

It is also advisable to know the conditions in which you will operate, whether in extreme conditions, or with gloves; at the indoor range or in the wild. Do I need long battery life? Or transparent protective caps through which I can aim immediately even without opening them? As already described above, closed models or container constructions are suitable for extreme conditions. Models with solar cells and/or shake-awake function (automatic switch-on/switch-off) can save batteries and simple control buttons make use with gloves much easier. 

Another important question: is there a suitable assembly for my weapon? Before buying an optoelectronic sight, it should be clarified whether the manufacturer can supply a mount that corresponds to the weapon and its requirements, or whether a special format is required from the gunsmith. 

Determining the eye relief is only limited, if at all, by the mounting options on the weapon. When buying, always make sure that your new reflex sight restricts the field of view as little as possible, without neglecting lens protection. Depending on the application, open reflex sights with 24x32 mm lenses or tube reflex sights with a diameter of 20-30 mm are useful.

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