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Old 11-27-2020, 11:59 AM
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red dot parallax



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I put this post in the proper category and after lots of views there is not one single post with testing. I frequent this Mark II section owning three of them so tell me what you think and if you can, test some of yours and report here please.

Thanks

https://www.rimfirecentral.com/forum....php?t=1208325
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Old 11-27-2020, 04:37 PM
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It might help if you tell us what you're trying to determine. Every optic is going to have some amount of parallax except at a single distance to target it's been adjusted for.

An observation about the report you linked to: They appeared to do all their testing on folding tables. I'm not sure how accurate that testing can be compared to a solid bench setup. At least they made an effort to minimize human error by having multiple "testers" for each scope.

In the end, I suspect human technique and ammo variance are much bigger players in RDS accuracy than parallax error. I hope you find the data you're looking for.
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Old 11-27-2020, 07:05 PM
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yes

You are correct that my wiggle and ammo have more to do with my inaccuracy than the average apparent parallax in my red dots. What was surprising was to find 4 1/2" at 25 yards in the model I sent back to the factory. In my three different brands they all have a little but the Vortex Venom 3 MOA seems best with 1/2" or less at 25 yards. Knowing this along with finding out other brands with little to none would be a good starting point as I use these for precision work not just hitting an 8" plate as fast as I can at 10 steps.

I was surprised to find this with the industry motto that they are parallax free. In some respects I do not think it is parallax but aberrations in the glass used. Again no such thing as a Parallax Adjustable Red dot. Why, it does not exist. Only varying degrees of quality control.
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Old 11-27-2020, 09:03 PM
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Quote:
Originally Posted by Test_Engineer View Post
It might help if you tell us what you're trying to determine. Every optic is going to have some amount of parallax except at a single distance to target it's been adjusted for.

An observation about the report you linked to: They appeared to do all their testing on folding tables. I'm not sure how accurate that testing can be compared to a solid bench setup. At least they made an effort to minimize human error by having multiple "testers" for each scope.

In the end, I suspect human technique and ammo variance are much bigger players in RDS accuracy than parallax error. I hope you find the data you're looking for.
Reflex (i.e. "red dot") sights are single plane. They aren't supposed to suffer from parallax.
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Old 11-27-2020, 11:32 PM
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Hawkmoon

I agree completely that there is no such thing as parallax in a dot scope. We are simply using that terminology as it looks, feels and smells like the same stuff we can experience in a rifle scope. The most important point to make here is that I have been doing this thing for decades and never tested my dot scopes for movement at the average distance I was using them.

Has anyone here tested theirs yet? It was a complete surprise to find out how much was in the three different brands I own. Again if you are just shooting large plates at a short distance you will continue to do O.K. However I prefer to use something with 1/4" at 25 yards vs 4 1/2"!
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Old 11-28-2020, 08:11 AM
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wikipedia covers it briefly. parallax exists in both red dot sights and reflex sights, its called parallax, and its real. If it says parallax free its at one distance or it has an optical system designed to reduce parallax
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Old 11-28-2020, 09:19 AM
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Its OK to call it parallax in a red dot/reflex as we all understand what that is. Not sure there is a single word to describe its problem. It could also be called "glass aberration causing apparent reticle/dot movement at distance".

A scopes parallax is due to a focal length where it is perfectly in focus without reticle movement parallax at one distance. That is why when you adjust a scope with parallax adjustment front or side you now change the focal length to a new perfectly in focus without parallax distance.

None of the red dots/reflex sights with 1X magnification work like a scope that is why none have an adjustable PA.

Has anyone checked theirs yet? Knowing what you have is the beginning of wisdom on this subject!
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Old 11-28-2020, 09:54 AM
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No such thing as parallax in a red dot sight. Parallax occurs in a scope because the reticle and the objective lens are on different physical planes separated by several inches or more. Adjustable objectives or side focus devices are used to place them on the same plane optically. Since a red dot sight projects the dot onto a single lens they are already physically on the same focal plane, so parallax cannot exist.

Last edited by Mike_AK; 11-28-2020 at 10:00 AM.
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Old 11-28-2020, 10:09 AM
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Originally Posted by Mike_AK View Post
No such thing as parallax in a red dot sight. Parallax occurs in a scope because the reticle and the objective lens are on different physical planes separated by several inches or more. Adjustable objectives or side focus devices are used to place them on the same plane optically. Since a red dot sight projects the dot onto a single lens they are already physically on the same focal plane, so parallax cannot exist.
do us all a favor and update wikipedia
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Old 11-28-2020, 10:14 AM
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do us all a favor and update wikipedia
Perhaps you could ask Wikipedia to update physics. Objects on the same focal plane do not exhibit parallax. Neither do objects on the same physical plane.

Last edited by Mike_AK; 11-28-2020 at 10:27 AM.
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Old 11-28-2020, 10:40 AM
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straight from wikipedia

Non-magnifying reflector or "reflex" sights have the ability to be theoretically "parallax free." But since these sights use parallel collimated light this is only true when the target is at infinity. At finite distances eye movement perpendicular to the device will cause parallax movement in the reticle image in exact relationship to eye position in the cylindrical column of light created by the collimating optics.[32][33] Firearm sights, such as some red dot sights, try to correct for this via not focusing the reticle at infinity, but instead at some finite distance, a designed target range where the reticle will show very little movement due to parallax.[32] Some manufactures market reflector sight models they call "parallax free,"[34] but this refers to an optical system that compensates for off axis spherical aberration, an optical error induced by the spherical mirror used in the sight that can cause the reticle position to diverge off the sight's optical axis with change in eye position.[35][36]

I agree with this 100 percent. the section on physics aint too bad either

Last edited by wonshott; 11-28-2020 at 10:42 AM.
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Old 11-28-2020, 11:15 AM
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Quote:
Originally Posted by jazzsax8
Its OK to call it parallax in a red dot/reflex as we all understand what that is. Not sure there is a single word to describe its problem. It could also be called "glass aberration causing apparent reticle/dot movement at distance".
Exactly right!

The problem starts with the fact that a theoretically parallax free plane is infinitely thin. In reality, an RDS scope uses a lens of finite thickness that the dot is projected onto. Lenses will shape/bend/redirect light. So they're designed to approximate a focal plane as perceived by our eyes. But errors (introduced by glass imperfections, design tolerances, and assembly methodology) will create apparent dot movement at different ranges.

Technically not parallax, but similar enough to share the term IMO.
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