How a Red Dot Sight Works

A red dot reflex sight is one of those simple inventions that drastically and forever change the way you do things. With a red dot mounted on your gun, aiming at short and medium distances becomes a no-brainer task. You just align the red dot with the target until they overlap, and then pull the trigger. Easy. But how does a red dot sight work? Let’s find out.

Red dot sight construction

The design of a red dot sight is based on a typical reflex sight and is extremely simple. The construction consists of a collimator – a semi-transparent lens, and an LED light. One side of the lens allows the entire light from a target to pass through the glass into your eye. And the other side of the collimating lens is made reflective. Thanks to the silvered multilayer coating, this side only reflects the red part of the spectrum, so the overall brightness of the target image remains almost intact.

Red dot sight operation principle

The LED light is powered by a small battery and emits light towards the collimating lens. The lens focuses the red dot reticle on the sight’s glass seemingly on top of the image of a target.

The reflective side of the lens has a concave form, so it focuses light rays coming from the LED into the “infinity”. This means that at infinite range the red dot will appear exactly over the target no matter at what angle you look into the sight. In reality, however, the range is finite, so the red dot may have some parallax at shorter distances (15-30 meters depending on the model).

What you should know about red dot sights

You can use red dot sight with both eyes open

Unlike other types of optical sights, a red dot sight does not require you to shut the idle eye. In fact, you better keep it open so you can see more surroundings and lead the target better.

Do not confuse a red dot sight with a holosight

Both types of aim assistance devices are technically reflex sights. However, a red dot sight does not contact the holographic grating. Hence, unlike holosights it produces a simple 2D image of the reticle – a dot, or a more complex shape.

You can use a red dot optics with a magnifier

If you want to increase the range with a magnifier, you can mount it to your gun together with the red dot sight. But make sure to mount your magnifier before the red dot, not after it. Also, select a smaller size of the red dot to make sure it will not overlap too much of the target in the sight. Another thing to keep in mind is the increased parallax shift when working at larger distances, because it can affect shooting accuracy.

You can use a red dot sight at night too

Some red dot sights come with a night vision option. But otherwise you can just use any night vision goggles with your red dot sight. Just set up the proper brightness of the dot depending on lighting conditions.

There are closed and open designs

Closed casing offers better protection from dirt and water. A red dot sight with a closed design (also called a tube red dot) is very similar to a classic rifle scope by they way it looks. The open design is... well, open. It features an open lens mounted to the sight with a small inclination of the aiming line. Needless to say, such design as more fragile and is more vulnerable to dirt, or to shock damage. On the other hand, open design of the red dot offers simpler aiming, even if a gun-user looks at the sight at an angle.

Red dot sight VS holosight

Both reflex sights can drastically improve your aiming. They are very close in terms of functions and they often even look similar. But what is the difference between them? Should you prefer one over the other?

• Price. The winner is a red dot sight, because it is much more affordable. There are no multiple mirrors inside it, and no holographic grating is required either. Also, a simple LED is also cheaper than a laser-emitting diode in a holosight.
• Accuracy. Both a red dot sight and a holohraphic sight are accurate at short range with the accuracy slowly degrading over the distance. Both have virtually no parallax distortion, but that depends on the model. So, it is a tie.
• User-friendliness. A red dot sight can be used with both eyes open, which is convenient. But holosight project a 3D reticle onto the same optical plane as the target’s. This makes aiming a bit easier and faster.
• Size. Red dot sights can be very compact and can fit even pistols. Holosights are usually larger and more weighty.
• Aiming speed. A red dot sight is unbeatable at quick aiming. The device was designed for instant aiming and shooting. You see the red dot, you pull the trigger. Holosights are slower, but not as slow as scopes.
• Battery life. Red dots win here with a huge advantage. A typical red dot sight can work 20,000 hours on the same battery, which means you can replace the battery like once in a year or so without even turning the device off between shooting sessions. Holosights consume more power so their battery life is about 1000 hours only.

What a red dot sight is best for?

Taking into account its merits and disadvantages, the optimal applications for a red dot sight are hunting and shooting at shorter ranges, for example in close quarters. The red dot offers quick aiming thanks to easily visible red dot reticle and virtually zero parallax error. A better overview of surroundings allows you to stay aware of the situation, which is also helpful during a hunt or a tactical mission.

If you need consultation on what type of red dot sight is the best for your specific purpose, please don’t hesitate to contact Battle Steel®️. We will be happy to help you make your choice.