What Is a Prism Scope? Doing Away With Traditional Lenses to Focus an Image

The ideal goal of every shooter is to achieve a one-shot kill. For those shooters who only concentrate on paper targets, their ideal goal is to hit the target exactly where they intended to hit. The chances of achieving the ideal goal are greatly enhanced when shooters choose to mount and use scopes on their firearms. The question then becomes, should they do away with traditional lenses to focus an image or should they try a newer alternative? Read on to discover the answer to the question 'What is a prism scope'?

​What Is a Prism Scope?

A prism scope is an aiming device that uses a prism to focus an image coming through the scope rather than the series of lenses used in a traditional scope. Prism scopes are usually more compact and limited to the lower range magnifications between 1X and 5X. Size and lower magnification range makes them ideal for tactical rifles such as AR-15s. They often serve as alternatives to other short-range optics, such as red dot sights.

The best way to answer the question 'What is a prism scope?' is by breaking down the basic concept of a prism scope and comparing and contrasting it to a traditional multi-lens scope. The advantages of doing away with traditional lenses to focus an image by utilizing a prism scope can then be discussed.

​What Is a Prism?

Those of you sharpshooters out there that can already answer the question 'what is a prism scope?' may need to take a break while we begin at the beginning. In geometry, a prism is a figure that has two similar, equal end-faces, parallel rectilinear figures and parallelogram sides. For this discussion, a prism is a glass or other transparent object the shape of a triangular prism with refracting surfaces at acute angles to each other so that white light is separated into a spectrum of colors.

 What Is a Traditional Multi-Lens Scope?

In order to answer the question 'what is a prism scope?' we need to compare it to the traditional multi lens scope.

Lenses

A traditional rifle scope is similar to a miniature telescope. A series of lenses within the tube or body of the scope focuses light in a specific location. The lens closest to the end of the barrel is called the objective lens. The lens closest to the shooter is called the ocular lens. The purpose of the objective lens is to transmit light back to the ocular lens. The ocular lens magnifies the light from the focal point.

Reticles

When the shooter looks through the ocular lens, the light illuminates the focal point of the target. Rifle scopes also have reticles, which are also called the crosshairs. These are markers inside the scope that show the shooter where the shot will go (hopefully) once the trigger is pulled.

​Magnification

Magnification is measured in X times your vision. When the scope is set to 5X, the image that is viewed will appear five times larger than when viewed without the scope. Most manufacturers set their rifle scopes so that they are focused at 100 yards. This means that the target should be clear when seen through the scope 100 yards away. Errors can occur with magnification.

​Eye Relief

Eye relief refers to the distance between the scope and the user's eye such that a full picture is visualized. The distance between the eye and the scope must be far enough so that when the rifle recoils after firing, it doesn't send the scope back far enough to hit the eye; this is called “getting scoped.”

​Parallax Issues

Parallax refers to a displacement or alteration in the apparent position of an object when viewed along two different lines of sight, as measured by the angle of inclination between those two lines. This means that nearby objects show a larger displacement or parallax than farther objects when observed from different positions.

Focal Plane

In terms of shooting, the focal plane of the target in the scope is offset from the reticle or crosshairs, creating a change in position of the target when the user shifts their gaze. Parallax is usually negligible in low magnification. Tactical style scopes such as the prism scope commonly measure at 100 yards.

 How Does a Prism Scope Work?

A prism scope works similarly to a traditional scope, but instead of lenses, a prism is used to focus the light. This creates a much more compact optic. Prism scopes usually have an etched reticle and an illuminated reticle.

​Etched Reticle

An etched reticle is made of glass with laser incised marks called hashmarks and bullet drop compensators. Etched glass tends to be more precise, because it allows for the customization of hashmarks and bullet drop compensators, and are much more durable than wire reticles.

​Illuminated Reticle

An illuminated reticle shows a red or green light point. It uses light to illuminate the point of focus. This enhances accuracy in low light and at night.

Advantages of a Prism Scope

Woman aiming a gun using a prism scope

image source: unsplash

Prism scopes are limited to lower range magnifications, typically from 1X to 5X. As previously mentioned, the compact size and lower magnification makes them suitable for tactical rifles such as the AR-15s. They are preferred by many shooters as an alternative to other short-range optic devices.

Prism

A prism scope provides a brighter, crisper and sharper image. This makes the acquisition of a target quicker. The prism is compact and lightweight.

Magnification

A prism scope allows for magnification, giving the shooter a larger site picture and extending the effective range, when compared to a red dot site. Magnification with a prism site is low when compared to a traditional scope.

Illumination

The illuminated and etched reticles give the shooter what they need to achieve their goal of achieving a one-shot kill. The etched reticle does not require batteries or fiber optics to be viewed.

Eye Relief

Prism sites need to be aligned with the eye and set at a certain distance away in order to obtain a clear image. In terms of eye relief, a prism scope has a relatively shorter distance. Unless the shooter requires extra long eye relief, this is an ideal situation.

Diopters

A diopter is a small dial or knob that allows the user to adjust the sharpness to match their own eyesight. This feature is a godsend for people with astigmatism or other eyesight deficits that make other scope types useless. Shooters who apply excessive diopter change usually experience more parallax issues.

Specificatunsplashions

Hand drawn retro telescope

image source: Freepik

Part of discovering what a prism scope is includes determining the specifications. Since there are different types and brands of prism scopes, we randomly selected one to describe. The specifications for prism scopes include more details than discussed here. This means that due diligence and adequate research will be required to decide which prism scope is ideal for any given person:

  • Battery Type = CR2032 3V Lithium Coin
  • Brand = Primary Arms
  • Click Value = 1 /2 MOA
  • Eye Relief = 3.70 in
  • Field View =1 0076.30 ft
  • Illuminated = Illuminated
  • Magnification = 1X
  • Manufacturer = Primary Arms
  • Night Vision Compatible = Non-Compatible
  • Reticle = ACSS Cyclops
  • Total Elevation Adjustment = 50 MOA
  • Total Windage Adjustment = 50 MOA
  • Turret Features = Capped Turrets, Tool Adjustable
  • Type = Fixed Magnification
  • Weight = 9.7 Oz

Is a Prism Scope the Best Option?

Man in black uniform holding a black rifle

image source:pexels

Depending on your needs, you may not want to do away with traditional lenses to focus an image. That is because a prism scope has benefits and drawbacks, once again depending on the user's needs. A prism scope is an aiming device that uses a glass prism to focus an image coming through the scope, rather than a series of lenses.

Prism scopes are limited to lower ranges of magnification; between 1X and 5X. This means that prism scopes are indicated for use to acquire targets that are at the short to medium range. Prism scopes are ideal for tactical weapons intended for use at close to medium ranges, for example between 25 and 50 yards.

The Goldilocks Range

Scopes that have too much magnification at close range will take time to visually acquire the target. Scopes that have too little magnification at longer ranges will fail to achieve a one-shot kill. The best advice that can be given about a prism scope is to practice. Learning to use your preferred scope in synchrony with the weapon it is attached to is the only way to determine the perfect range for you, in terms of your intended target.

 Bigger Is Not Better

Out there in the world of social media, advertising and male competitiveness, it's tempting to buy more magnification than necessary. Certainly, there are some very sexy and very high-powered, multi functional scopes out there to seduce the shooter, but just as you would not show up at a gunfight with nothing but a paring knife, shooters do not want to be in a situation where their choice of scope could result in a failure to achieve a one-shot kill or even a failure to save their life.