Differences Between Reflex and Holographic Sights

We do a lot of writing here about red dot sights, which for us is a broad term that encapsulates the wide range of ‘electronic sights’ available as upgrades to iron sights.  In this definition we’re talking about non-magnifying, rail mounted optics that have an illuminated reticle, usually in the shape of a dot.

Going by this you can see how a ton of different sights fall into this category.  But it is worth it to talk about two sub categories that sights also belong to: Reflex or Holographic.

These two different styles have the same core functionality, that is, creating an illuminated aimpoint that is overlayed onto a target for accurate shot placement.  Slight differences come in how the reticle is generated, and how the user may perceive its appearance.

Projection System

A reflex sight utilizes and objective lens and an LED to create the reticle within the sight window.  The objective lens works as a partial mirror that reflects collumated light from the LED back into the shooters vision.

The lens is designed to only reflect the red wavelength of the LED so the rest of it is transparent to view down range.

A holographic sight uses a laser diode and mirrors to illuminate a holographic reticle that is etched into the viewing window. The laser light gives the hologram its brightness and allows it to be seen against the contrast of the background.

Size & Shape

The projection system has a direct effect on how the optics are laid out, and therefore effect how all of the components fit into something that can be mounted on a rifle.

For reflex sights this means a tube configuration.  This is a style shooters who have used magnified scopes should be familiar with, albeit much shorter.  The objective lens is housed within a cylindrical tube that is usually around 30mm in diameter and a couple inches long.  Windage and elevation knobs are lined up on the bottom and top of the tube.

A holographic sight has a slimmer profile because it does not need the same focal length of the reflex sights due to its configuration of internal mirrors.  You will see that holographic sights have a square viewing window with a shallow depth, only ~0.5″ wide.  The rest of the components are held within the base of the optic that is closest to the mount.

Battery Life

Either type of sight will definitely last you a long time or any practical purpose, but the red dot sight has a clear advantage in the long run.  Its LED pulls 0.6 mA of current which will last 50,000 hours, even in inexpensive red dots.

On the other hand the laser of a holographic sight pulls 200 mA of current which brings it down to 500-1000 hours of battery life.

For someone who is shooting a handful of hour a week this shouldn’t be too much of an issue, but leaving a holographic sight running accidentally after storing it away will be annoying to find the battery drained next time you take it out.

Reticle

The reticles of reflex sights are more versatile in shape and color than holographic sights.  Dots can be green or red and take the shape of single points, rings, or crosshairs.

A holographic reticle is different because due to its design the reticle appears to be floating downrange when viewing it though the optic window.  This takes the parallax down to zero for given distances.  The most popular holographic sights are designed by EOTech, who have a unique reticle composed of a 65 MOA ring with a 1 MOA dot in its center.

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