How Does a Red Dot Scope Work?

by Aaron Kopf
Red dot scopes are popular with semiautomatic rifles and pistols.

Red dot scopes are popular with semiautomatic rifles and pistols.

Firearms are precision devices created for the specific purpose of placing a slug of metal in a particular location at supersonic speeds. For this reason, gun sights receive significant attention from gun enthusiasts. Some claim that iron sights are the only fail-safe option, while others place their trust in optical scopes. More recently, electronics entered the picture with the red dot sight, as known as the reflex sight.

Basic Function

Like any scope, a red dot sight features a concave lens in the back of the device. The lens gathers incoming light from a larger area than the human eye, presenting the illusion of magnification. Red dot sights additionally contain an internal laser that points at the center of this lens, reflecting off a thin layer of reflective coating at a specific angle to create a red dot floating in the center of the magnified image.

Dot Adjustment

This red dot can be adjusted for targets at different distances. Like all objects, gravity causes bullets to drop as they travel. To compensate, firearms must be aimed slightly higher for accuracy at greater distances. Similarly to scopes of other types, the red dot is adjustable vertically (elevation) and horizontally (windage) via knobs or screws on the side of the scope, depending on the model.

The Parallax Problem

The parallax problem concerns the way a shooter looks into a scope. Using a traditional scope, if a shooter does not have the aiming eye and scope center lined up, the cross hairs will not aim squarely at the target. This is to say, the bullet may land in different places depending on where the aiming eye was located in relation to the scope center. Contrary to popular belief, red dot sights suffer from the same problem. The only fix is to ensure proper eye-scope alignment.

Optional Filters

Similarly to sunglasses, red dot sights can be altered through the application of filters. One of the most popular filters is the polarization filter that attaches to the front of the scope. One of the disadvantages of the red dot sight is that it can be very difficult to see the dot on very bright days. The polarization attachment filters out the brighter rays of light entering the scope, eliminating glare and other reflections.


The red dot sight allows quick target acquisition, optimal viewing in a variety of lighting situations and removes the visual obstacle of iron sights. For these reasons, red dot sights are popular with military units, particularly special operatives. Red dot sights are also popular with less-experienced shooters and those with failing vision. Red dot sights are not typically used by sharpshooters, as the scope power is not significant enough for long-distance fire.

About the Author

Aaron Kopf graduated from the University of Central Arkansas with honors in 2009, holding a Bachelor of Arts in communication. While enjoying his time at college, Kopf was published in The Echo and Vortex magazine.

Photo Credits

  • semi automatic handgun image by jodi mcgee from