Optics on pistols and long guns are as prevalent and varied today as the firearms themselves. Any purchase of a long gun is nearly always followed by the owner venturing down the proverbial optical rabbit hole. The options, designs, and relative price points are endless. In most instances, a fixed power electronic sight is an attractive option to fill the niche for defensive and competition applications for the benefits of rapid sight picture and target acquisition.
The two most basic optics available for electronic sights are red dot, or reflector (reflex), and holographic. At a passing glance, these two optic designs appear relatively similar in design, purpose, and function. However, these optics are profoundly different. Before delving into a direct comparison between the two designs, we need to understand how these optics function.
The Red Dot Reflexive Sight
A red dot (reflexive) sight is an exceptionally simple design. Reflex dot sights utilize a single diode, commonly a red (sometimes green) LED emitter, that is positioned at an angle to a pane of coated glass. The diode is then projected against the glass. The coating on the glass reflects the diode back at the user so they can see the LED, which is projected as a dot or other reticle to the user. This acts as the sight.
Red dot sights are commonly found in two styles: closed and open emitter. The open emitter design; such as the Trijicon RMR, Vortex Venom, Holosun SCS, or Burris FastFire; has a single piece of coated glass with the diode exposed to the elements. This provides for a smaller footprint and less weight, making this design popular for handgun optics. Unfortunately, the open emitter design can allow dust, dirt, water, Cheetos, etc. into the area where the diode is located or into the optical window. This presents obvious complications for the optic and can affect the sight picture. The closed emitter design — such as the Vortex Strikefire, Aimpoint T1/T2 and PRO, Holosun 509T, and Trijicon MRO — mitigates this issue by adding a second pane of glass that encloses the diode in a protective shell.
Holographic optics have a more complex design than a classic red dot sight. Instead of an LED emitter, holographic sights use a laser to project the image through a series of mirrors into the viewing plane for the shooter. Due to their complexity, holographic sights are larger than red dot sights. There is a limited selection of holographic sights available. To date, EOTech and Vortex are the only companies I know offering reliable holographic sights.
With complexity comes a price. Holographic sights are consistently more expensive, in the $600-800 range, than most readily available red dots. Nevertheless, reflex red or green dot optics carry a wild range of pricing, from $50 to $800, that correlates to the product’s durability, battery life, clarity, etc. While reliable red dot optics can be purchased in the $200 range, like a Vortex Sparc, more expensive red dots, like the Aimpoint T2, carry a heftier price tag. Holographic sights, due to their design, don’t currently carry a cheaper price tag.
Laser technology has improved substantially over the last 50+ years. Unfortunately, while quality has improved, there is a limit to energy consumption with a laser versus an LED diode. The Vortex AMG and EOTech feature respectable battery life in the 500-1,000 hour range while being powered by “AA” or CR123 batteries. Conversely, red dot optics feature battery lives in excess of 25,000-50,000 hours on similar batteries, or smaller. Some red dot optics, like the Aimpoint T1 and Bushnell TRS-25, run on CR2032 watch batteries. I own several Aimpoint T1s with battery lives exceeding a year of Constant On.
Unfortunately, holographic sights don’t have the technology available to meet the extended battery life of red dots. In my prior training with a patrol rifle, the rifle is normally stored “patrol ready” which is safety on, empty chamber, and loaded magazine. When deploying the rifle, I’ve trained to charge the rifle and turn the optic on in one smooth movement. For most home defense, law enforcement, and competition purposes, the battery life issue is relegated more to needing to purchase/change batteries more frequently.
Red dot sights, due to the simplicity of their design, can provide a smaller footprint and weight than holographic sights. With the rise in popularity of handgun optics, some red dot sights are as light as a few ounces while holographic sights have been relegated to rifles due to their size. The need for a laser source, mirrors, and multiple glass windows require a larger footprint. Even the smallest holographic sights (EOTech XPS2 for instance), still carry a weight of 9 ounces with a 4” x 2” x 2.5” footprint. Some of the smallest handgun optics, like the Trijicon RMR or Holosun series of red dot optics, have a 2-3 ounce weight with a 1.5” x 1” x 1” footprint.
Optical clarity and appearance on a red dot optic versus holographic are, in my opinion, arguably more important than battery life or optic size. Holographic sights have a distinct advantage over red or green dot sights — starburst. Starburst is an optical appearance where the intensity of the “dot” on a reflex sight causes the reticle to distort at higher intensity settings. Figure 1 is a side-by-side comparison of an Aimpoint T1 and Vortex AMG UH-1 Gen II “Huey” at the appropriate brightness settings for available light. The reticles on both are relatively crisp and clear. Comparatively, Figure 2 is both optics at their maximum brightness setting under the same light. The Aimpoint’s reticle, while not done justice in the images, has a larger dot size and is distorted in a pattern similar to a star. The holographic sight’s optic is more intense, but the detail of the reticle is still clear and undistorted.
Why does starburst matter? This distortion makes clarity and precision more difficult, especially when used with a magnifier. Furthermore, for those unfortunate souls with an astigmatism, red dots can present more issues for the user that are aggravated by night or low light conditions. The inherent design of a holographic sight avoids this complication.
The reticle of a red or green dot reflex sight is limited by the size of the diode. Thus, most red dot reticles are limited to approximately 3 MOA. Holographic optics are constrained by our own eye’s ability to see the reticle. Thus, holographic sights frequently achieve 1 MOA dot sizes with more complex reticle designs like range markers. Examples are the 1 MOA dot and larger (30-60 MOA) crosshair style circles and Vortex’s CQB triangle design.
Red dot sights and holographic sights are inherently faster; hence their popularity over iron sights. For those of us trained in fighting with an iron-sighted pistol, there is a reason why we are taught to focus on the front sight. Despite the common belief that we can multitask, we really can’t. The brain can only focus on one thing at a time. It’s the same with our eyes. Our eyes don’t have the wide depth that field cameras and can only focus on a single focal plane. Therefore, we are taught to focus on the front sight.
Red dot sights require the shooter’s eye in the sight plane to focus solely on the dot. Is it faster target acquisition? Absolutely. However, holographic sights superimpose the reticle onto the sighting plane and allow the user’s eye to focus on the target AND reticle without an observable difference between the two.
This observation also brings up another interesting difference in red dots versus holographic sights — magnification. The holographic sight superimposes the reticle onto the target as a hologram. Accordingly, the dot size remains the same regardless of the magnification on a holographic sight whereas the dot size on a green or red dot is affected by magnification. A 2 MOA dot under 4x magnification will become an 8 MOA dot on a red dot. For holographic sights, the MOA size for the reticle remains the same regardless of magnification.
Making a Decision: Red Dot or Holographic?
The intent of this article isn’t to make the decision for you, the end user, when purchasing an optic. Every variant of a reflexive red dot sight or holographic sight serves a purpose. Cost, durability, application, battery life, vision, sight picture, reticle, etc. are all important factors in determining optic selection.
Ultimately, it’s upon the buyer to make an educated decision based on their needs, abilities, and pocketbook on what optic they will purchase. Personally, I have no dog in the fight on what kind of optic I would offer as a blanket recommendation. I own virtually every kind of design available: closed emitter, open emitter, magnified dual power fiber optic, low power variable optic (LPVO), high power variable optic, and holographic. Each one of those sights is dedicated to a use and purpose I’ve found within my collections of tools and toys. The end goal is to be competent and capable with each platform and know the limitations and applications.