A Primer on Parallax at Breach Bang Clear – Nothing is Truly “Parallax Free”

parallax-explained

Red Dot and no-magnification optics are probably the greatest increase in efficiency for firearms outside of the invention of the brass case. Using them greatly increases the chance of getting solid hits on target, as it removes the mental and eyesight gymnastics of aligning four objects into a single plane, reducing it to three.

However, like their magnified optic cousins, red-dots also suffer from parallax, which typically appears at short-ranges when the eye is not centered through the optic. For those not familiar with the term, parallax refers to “the effect whereby the position or direction of an object appears to differ when viewed from different positions, e.g., through the viewfinder and the lens of a camera. (courtesy of Google Dictionary)”

Breach-Bang-Clear has put together an excellent primer on parallax staring with the basic explanation of just what is parallax?

Then, they proceed to test some of the most well-known optics including:

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

Parallax is easily on nearly all of the optics:

Breach Bang Clear also goes into detail on a few other topics that effect red-dots such as refraction (the apparent displacement of an object as light travels through medium) and aberration.

Check out their great primer over at Breach Bang Clear.  

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Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at Nathan.S@TheFirearmBlog.com

The above post is my opinion and does not reflect the views of any company or organization.


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  • A Fascist Corgi

    One of the things that I noticed is that I’d never experience parallax shift with my red dot sight if I co-witnessed the red dot with small aperture iron sights. Anyone know why that is?

    • Roy

      Because then your eye is properly aligned with the optic

      • A Fascist Corgi

        Yeah, that’s what I assumed was happening. Co-witnessing my red dot sight with a small aperture iron sight forces me to always have my eye properly aligned with my red dot sight. That’s why I never followed the popular trend within the gun community to fold my iron sights down when using a red dot sight. People say that iron sights block too much of their field of view when using a red dot sight, but I don’t find that to be true at all. The only thing I noticed is that my field of view tends to darker because the iron sight is blocking light.

        • Toxie

          If you’re using your rear sight still, you’re rather negating the point of the red dot as you’re still having to align the sights with the target to see your dot. Not optimal, and the rear site is certainly blocking quite a bit of your FOV.

          • A Fascist Corgi

            Mmm. Not really. The red dot is still easier to see than the front sight post. I don’t find the co-witnessed iron sights slowing me down at all. And what’s the point of using a red dot sight if parallax is causing you to miss? And like I said, my POV is perfectly fine when using iron sights. The only minor downside is that your POV will be darker. Go give it a try. You’ll see that leaving your iron sights up while using your red dot sight works great.

    • Pseudo

      I guess I would need to know exactly what you mean by co-witnessed here. If you’re pretty close to aligned with your irons, there would be essentially no parallax effect at all on the dot because you would already be properly aligned.

  • Sarig

    “Red Dot and no-magnification optics are probably the greatest increase
    in efficiency for firearms outside of the invention of the brass case.
    Using them greatly increases the chance of getting solid hits on target,
    as it removes the mental and eyesight gymnastics of aligning four
    objects into a single plane, reducing it to three.”

    Do you have any actual data on this?

    • Alex

      Norwich University study on RMR vs irons on handguns come to mind.

      • Sarig

        Cheers! It’s not exactly published research, but it’s more than the “common sense” argument presented in the OP.

    • IndyToddrick

      Do you not see the significance in speed that comes from removing the need to align front and rear sights? Or from being able to aim your weapon from an angle without even looking down the barrel? It’s a pretty big deal. If you can see the dot on the target you can hit the target, even if you are holding the gun over your head in the air.

  • Major Tom

    Four objects? I’ve always thought of iron sights as aligning only one or two.

    • marine6680

      Eye, rear, front, target.

  • marine6680

    Unfortunately, that last video was not helpful.

    The target and dot are not in focus for some of the optics they show. All you can try to do is attempt to mentally track the position of the target.

    What then happens is that it seems the red dot is way off, or moving, When in reality, refraction within the sight is causing the target to appear in a different location.

    There were times the shift in apparent position was pretty drastic.

    If they could not get the shot to focus well, another method of holding the optic steady, and aimed at the target, and then shifting the camera around may work.

    I have done similar checks on optics myself, mounting the optic or rifle on a block, aimed at a target at the proper distance, and then shifted my head position usually from a few feet way, and watched the dot.

    I have found a faulty optic this way, that got sent back to the manufacturer for replacement. I was having a hard time getting a good 50yd zero, after checking the optic I found this issue. So it turned out that little changes in the alignment of my head, caused big shifts down range.