No Such Thing As Parallax Free

parallax_free_social

Dave Merrill of Breech Bang Clear explains that there is really no such thing as parallax free. He breaks it down rather simply and it is easy to grasp.

 

Here is a photo that illustrates how the reticle is reflected in the optic.

parallax-red_dot_function

 

 

Most of the time a shooter will not experience much parallax shift if they have a good solid and consistent cheek weld. The issues comes down to unusual shooting positions and the focal length of the dot in relation to the target.

 

parallax-explained

 

Here is a very simple yet clear demonstration of how this works.

 

How do manufacturers deal with parallax? Here is Merrill’s explanation.

Have you ever seen 1x RDS with a parallax adjustment turret? Me either. There are several different methodologies that manufacturers employ to reduce parallax. One of them is focusing at infinity. Remember that perceived movement at longer ranges is reduced. A dot focused at infinity will have less apparent movement, especially with targets further than 50m away or so, than a dot focused at a closer range. A red dot sight with a smaller objective window will also have less parallax, simply because your vantage point can only deviate so much before you’re out of the window entirely. Many reflector setups will utilize a Mangin mirror, which is a concave lens that helps to ensure the dot stays in line with the body itself. This setup is especially useful for reducing parallax from lateral movement, though they still remain susceptible to deviations in vertical movement. No doubt there are several more methods.

Merrill does test this himself. Using a picatinny rail, a vice and a camera sliding rig he sets up some red dots and a target out at 68m. Here are the optics he tested.

  • Aimpoint Micro H1 (4 MOA)
  • EOtech EXPS
  • Trijicon MRO
  • Leupold LCO
  • Trijicon RMR 01 (3.25 MOA)
  • $40 Tru-Glo Walmart Special

To check out Merrill’s article click here.



Nicholas C

Co-Founder of KRISSTALK forums, an owner’s support group and all things KRISS Vector related. Nick found his passion through competitive shooting while living in NY. He participates in USPSA and 3Gun. He loves all things that shoots and flashlights. Really really bright flashlights.

Any questions please email him at nicholas.c@staff.thefirearmblog.com


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  • LG

    The mathematician knows that the solution can not be reached. The engineer knows however that he can get close enough for practical purposes.

  • stephen

    Even though the folks at burris say their FastFire III is 1x magnification when you read the manual it says the magnification is 1.07. When you look through it you see the difference.

    Sometimes ‘close enough’ is ‘good enough’.

  • They are a mystery to you but you say the writer doesn’t know what they are talking about!

    • Shocked_and_Amazed✓ᵛᵉʳᶦᶠᶦᵉᵈ

      But is he wrong about the subject matter of non holographic red dots? Just curious

      • Matt Wilder

        As I understand it, the original poster is correct, while admitting his flaw that he knows little about the holographic type weapon sights. It IS possible to know about one subject, and not the other without having to be an expert on both. Those that can admit as such are better any day than those that claim they are experts of all. Just because I know how to fly aircraft and even how to build them does NOT make me an expert or qualify me to talk about the electrical engineering behind avionics sub-systems, and I’ll be the first to tell you that.
        He merely questioned the author’s understanding of parallax in relation to and the effects on red-dot sights. He made NO claims to understand parallax with holographic sights.

  • Treyh007

    As long as my Eotech, AIMpoint and Mepro hit where the dot is pointing I’m fine with the “parallax free” fine print.