School Me On Parallax

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coleman1495

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Hello,
I have been doing a bit of thinking about parallax and its effects on accuracy. I currently have a Vortex Diamondback 2-7x35 rimfire scope mounted on my 22lr rifle. This scope is factory adjusted for parallax at 50 yards.

This is my understanding of parallax:
If a person is looking down the scope their head is not completely parallel to the rifle scope. They are viewing it effectively from a slight angle as their head is inevititably of to one side slightly. This causes the reticle to appear off center (or to the left) slightly. If the scope if adjusted to 50 yards and the person is aiming at 50 yards then the reticle should be centered. If the person was to aim at a closer distance then the reticle would appear left of target. If the scope had an adjustable parallax turret the person could simply adjust it down to the new distance.

Lets say I set my rifle down down so it is stationary and free from my movements. If I look through the scope and move my head from side to side the reticle appears to move on the target. The movement of the reticle is fairly significant especially at closer ranger like 25 yards. Even at 50 yards the movement is well over an inch. I have learned that keeping my head in a consistent spot between shots is essential in obtaining tight groups.

Would the amount of movement in the reticle be fairly constant with all scopes? If I were to purchase a higher end scope would the movement of the reticle be minimized?
 
Scopes with non-adjustable objectives set at the factory are always going to be a little hit or miss. The fact that the reticle is moving means this scope isn't parallax-free at 50yds.

That being said, you'd be hard pressed to find a higher end scope that isn't adjustable.

If this 22 is just for plinking, and you're not trying the 50yd rimfire challenge, I wouldn't worry about it.
 
The scope is not parralax free at the 50 yd distance you were using. Whether your own measurement is off or the parralax setting in the scope is off I don't know. Once parralax is dialed out there will be no movement between target and reticle when you move your head. Move your target distance until you find where your scope's parralax is adjusted to.
 
So just to be clear, you are stating that if a scope is adjusted for a given distance it is parallax free at that distance? I am not sure that my scope has no parallax at any distance. If I aim at a given point and move my head from side to side the reticle always moves no matter the distance.
 
I believe that if your scope is closer to the rifle the parallax is reduced. As you get closer to the target, the effect of parallax would increase also.
 
MikeinCalgary said:
I believe that if your scope is closer to the rifle the parallax is reduced.
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That doesn't make any sense. If the scope is on a rifle, or is bolted to a bench, there would be no difference in adjusting to remove parallax.
Parallax is created when the image of the target inside the scope tube is not located exactly on the reticle. It is entirely contained within the scope, there are no external factors involved.

As you get closer to the target, the effect of parallax would increase also.
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That's not true either. More likely that parallax is easier to see at shorter ranges.
 
A scope with adjustable parallax is supposed to "project" the reticle onto the plane of your target, as opposed to say 100 yards apart at sight in. On a fixed parallax scope, this is only correct at one distance.
 
Parallax or discrepency in focus is a result of different points in the light path at which the reticle and the target image are focused. It is essential with any rifle scope to initially make sure the eyepiece is adjusted to ensure the reticle is in focus. If the scope has an image focus or parallax adjustment on the objective bell or a side focus (third adjuster typically on the left side from the reticle adjustment turrets) this is then used to bring the image into focus with the reticle.
If the reticle cannot be focussed with the eyepiece when viewing on a nondiscript or blank background, I would suggest the scope is faulty or is not sufficiently precise for the task.
 
Alpheus said:
That doesn't make any sense. If the scope is on a rifle, or is bolted to a bench, there would be no difference in adjusting to remove parallax.
Parallax is created when the image of the target inside the scope tube is not located exactly on the reticle. It is entirely contained within the scope, there are no external factors involved.

That's not true either. More likely that parallax is easier to see at shorter ranges.
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You're probably right. I used to own a rangefinder camera (the window you look through is separate from the lens) and I just remember that if you took close ups with it the framing is off, but as you stepped back it got better (less parallax). And I assumed that if the viewing window was more separated from the lens then then that would make it worse; so coleman would be right in that case. But it probably is different on a scope.
 
The easiest way to picture parallax is to find a target and hold out a pencil out at arms length between you and the target. Move your head slightly and see the pencil tip move on the target. That is parallax. Now take the pencil and place it physically on the target and move your head. The tip no longer moves. That is parallax free. To be parallax free, both the reticle and the target have to be on the same focal plane.

If you move your head sightly (not so much as to cause shadowing) and the crosshairs move around on the target, you are not parallax free.
 
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Eotech has one piece of unmagnified glass. The parallax happens when your reticle and target are not inline. The eotech is always inline with target so no parallax error
 
DMS1 said:
A scope with adjustable parallax is supposed to "project" the reticle onto the plane of your target, as opposed to say 100 yards apart at sight in. On a fixed parallax scope, this is only correct at one distance.
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Adjusting the parallax moves the image of the target inside the scope tube until it conincides with the piece of glass the reticle is eteched on to. In kombayotch's analogy, the paper target is the image in the scope tube, and the reticle is the pencil.

Here is a page with some simplified diagrams that explain it well: http://www.6mmbr.com/parallax.html
 
Okay this makes sense to me. So if a scope is parallax free at 50 yards the user should experience parallax at distances greater or less than 50 yards? Would it be fair to say that if I should experience the same amount of parallax at 25 yards as 100 yards? The effect is more obvious at closer rangers so that would make sense.

I have a Razor red dot sight on one of my rifles. It shows virtually no parallax at any distance. I used to own a bushnell trs-25. That sight had fairly lousy parallax at close distances. Would a different and better quality scope than my current one have less parallax?
 
coleman1495 said:
Okay this makes sense to me. So if a scope is parallax free at 50 yards the user should experience parallax at distances greater or less than 50 yards? Would it be fair to say that if I should experience the same amount of parallax at 25 yards as 100 yards? The effect is more obvious at closer rangers so that would make sense.
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Yes, you'll experience parallax both at greater and shorter distances. See the diagram on the page linked by Alpheus.

For a scope set for zero parallax at 50yrd, parallax amount at 25yrd should be the same as for 75yrd: it's geometry with straight lines. But remember that parallax is an angular error: as with MOA, how many inches of error the parallax error translates to on your target depends entirely on how far that target is from the rifle. The closer you are to your target, the less parallax error will matter for your shot. A (for example) 0.2MOA parallax error at 50yrd is 0.1" but 0.4" at 200yrd and 0.8" at 400yrd.

Here's something practical I found on OpticsTalk.com:

Most brands of scopes that do not have a parallax adjustment are pre-set at the factory to be parallax free at or around 100 yards; rim fire and shotgun scopes are set at or around 50 yards. Most scopes of 11x or more have a parallax adjustment because parallax worsens at higher magnifications. Generally speaking parallax adjustment is not required for hunting situations and is primarily a feature used and desired by target shooters. A 4x hunting scope focused for 150 yards has a maximum error of only 8/10ths of an inch at 500 yards. At short distances, the parallax effect does not affect accuracy. Using the same 4x scope at 100 yards, the maximum error is less than 2/10ths of an inch. It is also good to remember that, as long you are sighting straight through the middle of the scope, or close to it, parallax will have virtually no effect on accuracy in a hunting situation.​


I have a Razor red dot sight on one of my rifles. It shows virtually no parallax at any distance. I used to own a bushnell trs-25. That sight had fairly lousy parallax at close distances. Would a different and better quality scope than my current one have less parallax?
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Red dot sights usually have the reticle set to infinity. Still, there is some parallax, and it is more pronounced at close range.
 
Okay so I did a little bit of testing. The Diamondback scope has noticeable parallax at almost any distance I view. It is most definitely is not parallax free at 50 yards or anywhere close to 50 yards. Its almost a couple inches if you exagerate your head movement. My Zeiss Conquest has hardly any parallax when I aim it at the same locations. She is pretty near rock solid when i move my head from side to side.

I guess that is the difference between a 200$ scope and a 500$ scope.Now to find a better scope for my .22lr
 
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