Parallax question...

[rushthezeppelin]

I recently picked up the PA 4-14x FFP R-Grid reticle scope and finally got a chance to take it out to BOTW today. One thing that I thought was a bit odd though was how I pretty much had to max out the parallax adjust at 750 and still wasn't getting completely parallax free, only about a 1/8th mil variation but still noticeable. At 1k it was getting closer to half a mil of variation. Does this possibly mean I set my diopter wrong? I tried to follow the instructions on setting up the diopter ring properly but really had a tough time finding a spot where it obviously seemed to be in focus (I think part of this might be that I possibly need to see an opthamologist). Should a properly set diopter ring mean the distances listed on the parallax adjustment would be more on target? The scope does have a 1k listing on the parallax adjustment right before the infinity setting so I'm confused whether this is user error or manufacturer error.

The good news is it didn't seem to affect me too badly as I did manage a fair number of hits at 750 and even got one hit at 1k today. Lucky me that the wind was a scant 1-3mph today

 

[HKShooter65]

Seems I recall that the maximum parallax error is 1/2 the objective oriface size.

To see this clearly look through a red dot like an MRM or Eotech or Comp-M2 or the like.
Look at something 5 feet away. That parallax seems huge as the dot moves around an inch.

Now look at something 50 feet away and move your head around.
Same inch matters very little.

Now look 100 yards.
Same inch is of no real consequence, as it's undiscernable with a 2-4 MOA red dot.

At 750 yards or 1000 yards for most of us.....
Meh. Mas or menos 1/2 inch. I wish I was that good.

........................................
So, now to be more germane to your post:
Same thing applies to a glass hunting scope and reticle with a fixed parallax at 100 yards.
It, the crosshair intersection, moves around either way up to 1/2 the objective diameter at 75 feet or 200 feet.
It's rock stable at the fixed/engineered 100 yards.
Hogs won't care.

In a Nightforce 12-42x with a huge objective shooting for 0.1 MOA on a 6mm bench rifle getting the parallax set to the right distance is a big deal.


HKS
I could be totally wrong, as I'm making this stuff up.

 

[dee]

Never trust the numbers on a parallax knob. Run untill it's the best you can get it.

 

[robertc1024]

Go to snipers hide. Learn.

 

[Dawico]

Really, for what those scopes cost that isn't too bad.

I don't believe there is a connection between the diopter focus and the parallax.

 

[rushthezeppelin]

So, now to be more germane to your post:
Same thing applies to a glass hunting scope and reticle with a fixed parallax at 100 yards.
It, the crosshair intersection, moves around either way up to 1/2 the objective diameter at 75 feet or 200 feet.
It's rock stable at the fixed/engineered 100 yards.
Hogs won't care.

In a Nightforce 12-42x with a huge objective shooting for 0.1 MOA on a 6mm bench rifle getting the parallax set to the right distance is a big deal.

Steel plates at 1000 yds seem to care alot though ^_^ At least I seem to be able to get my head in a pretty repeatable spot behind the scope though. I guess it actually helps that I'm right at the max eye releif for the scops as I can see the black start to bleed in on edges if I'm not perfectly centered.

 

[HKShooter65]

Steel plates at 1000 yds seem to care alot though .

Somebody correct me if I'm wrong. Old dogs can at least hope to learn new tricks.

The steel plates at 1,000 yards is really where parallax is of little/no consequence.

Here:
Scroll down to Example 2, paragraph 3.
http://rimfirebenchrest.com/articles/parallax.html
And notice the article is about close rimfire shooting where parallax might be noticeable.
Even with high precision distance benchrest shooting parallax is of decreasing significance.
Counterintuitive, perhaps.

Maximum parallax error is an absolute invariable function of exit pupil size,
It is NOT a percentage error that increases it distance.
It is a fixed absolute, so the effect, as a percentage error, diminishes at distance.

I had a large objective Nightforce on a .22lr (Ya, ya, silly) and an inch parallax at 15 yards on a head shot on a squirrel was a huge error.
The same scope, now on my FN Special Police .308 has, as a maximum, the same one inch at ANY distance.

If an inch parallax error at 500 or 1,000 meters make a difference to your steel shooting you are a far better shooter than I.

And as you already pointed out.....given a centered eye on the scope...... parallax error is always zero anyway.

 

[Dawico]

Think of parallax as a similiar function as MOA. It is a triangle starting at your eye and scope. 1" off at 100 yards, 2" off at 200 yards, and so on. So you are looking at 10" off at 1000 yards.

It stays the same percentage but the amount grows as the distance does.

You can adjust the percentage with your parallax adjustment but low end scopes may not allow a 0 percent error.

And yes, a perfectly centered eye negates the whole problem.

 

[rushthezeppelin]

After doing alot of searching I did manage to find someone who goes about the diopter adjustment in a totally different way. I don't think it will change anything as far as parallax goes but I think it's already showing me that I did not setup my diopter ring correctly.

Screw the eyepiece out (CCW) all the way, until it stops.
If you wear glasses, put them on.
Hold the scope up and look OVER the scope at the sky, and relax your eyes. Then move the scope in front of your eye.
The reticle should look fuzzy
Turn the eyepiece in 1/2 turn, and do the same thing again. You will have to do for a while before the reticle starts to look better. When you start getting close, then turn the eyepiece 1/4 turn each time.
Do this until the reticle is fully sharp and fully BLACK immediately when you look through the scope.
Than back off one turn and do it again to make sure you are in the same place.
Then LOCK the ring on the eyepiece, and leave it alone FOREVER!

 

[Dawico]

After doing alot of searching I did manage to find someone who goes about the diopter adjustment in a totally different way. I don't think it will change anything as far as parallax goes but I think it's already showing me that I did not setup my diopter ring correctly.

That is correct beside the "leave it alone forever" comment. As your eyes age and change you may need to readjust it.

 

[rushthezeppelin]

True enough. Like I said earlier too I think I might need to see an opthamologist. My eyes are very slow to focus after being closed, hence part of the reason I was having trouble setting up the diopter. Not sure how much can be done about that though. The method I found though did seem to make it markedly easier. Seems to have made a big difference having the ring fully out to start vs fully in.

 

[Jack Ryan]

If I may be so bold as to offer some suggestions concerning parallax and scope adjustments. This is just a cobbled cut/paste job from a couple of my own posts else where on the topic so if it seems a little jumbled, I think you can still get the jist of it. Don't take any of it personally or even specifically intended for any one I don't know the whole story about. It's just a rerun of a couple of posts I've offered else where I thought someone might be interested in.


Parallax is the dial on the front of the scope. Eye focus is the dial closest to your eye.

Set the parallax dial at infinity and the rear eye focus turned in like it was from the factory. With it set up on the rifle is easiest and best, empty the gun, point it at the sky and aim, open your scope eye and the cross hairs should be sharp, clear and in focus. If not start turning out the focus until they are.

Set the gun down a minute or two, blink a few times because staring dries your eyes and changes their normal focus.

Pick the rifle up and aim at the sky and repeat if they are out of focus when you FIRST look through it.

Repeat until the focus is set for the cross hairs to be in focuse and sharp for your eyes. This is easiest if you have something to rest the gun on and point it up while you do it.

The parralax will now probably be close to the marked indicators but probably not dead on.
Now to "fine tune" that parallax will bring groups in together to tell you what the rifle/amo is really capable of. Get your sand bag set up on a SOLID platform at a KNOWN distance target, say 100 yards. Set the front/parallax at 100, set the gun so it will stay by it's self at 100, on target. Now if that cross hair is moving around even the slightest bit on the target you can take that out of it most likely buy just very slight adjustment at a time of the front / parallax adjusting ring. Try to look through and test at the same time to see if it get's better or worse until the cross hairs are as little movement as possible. Be sure you are checking both up and down as well as left and right. It's not unheard of to be able to get one perfect and the other still a little out but you are just trying for the absolute best you can get it at the highest magnification at that distance.

Once you do this a few times and at different distances you'll start to notice for that individual scope it seems to "run" just a hair over or under the marked yardages on the front ring and it will really speed things up.

Scopes with 9x or less don't usually even have a parrallax adjustment because it's the higher power that starts making it change and those scopes are set for 100 yards permenantly. That's one thing you can do for a quick easy shot is to dial it down in power to 9 or under and I think that takes a lot of it out. This and not knowing the way these work would explain why a lot of new guys get to thinking the "jiggle" in a high magnification optics is what is screwing with their groups and sometimes they are good and sometimes they are bad.

 

[HKShooter65]

Think of parallax as a similiar function as MOA. It is a triangle starting at your eye and scope. 1" off at 100 yards, 2" off at 200 yards, and so on. So you are looking at 10" off at 1000 yards.

That's the common misconception.
Actually:
Reference this:
http://rimfirebenchrest.com/articles/parallax.html
Parallax error does NOT increase with distance.
It's maximum error is 1/2 the objective diameter at any distance. It's not the divergent angle function to which you are referring.

It's quite easy to demonstrate:
Secure your rifle.
Set the parallax as far wrong as possible
Move your eye all around behind the scope.
Maximum parallax error will be about the size of an oak leaf at ANY distance. 5 yards or 500 yards. It's maximum will be less than an inch. A constant.
It's constant and not increasing at variable with distance.
i.e. not increasing with distance.

With a 50mm (~2 inch) objective.....1" off at 20 feet......1" off at 200 feet........1" off at 2,000 feet.

That's why it matters to a squirrel at 20 feet but not to a steel plate at 2,000 feet.

 

[Dawico]

That's the common misconception.
Actually:
Reference this:
http://rimfirebenchrest.com/articles/parallax.html
Parallax error does NOT increase with distance.
It's maximum error is 1/2 the objective diameter at any distance. It's not the divergent angle function to which you are referring.

It's quite easy to demonstrate:
Secure your rifle.
Set the parallax as far wrong as possible
Move your eye all around behind the scope.
Maximum parallax error will be about the size of an oak leaf at ANY distance. 5 yards or 500 yards. It's maximum will be less than an inch. A constant.
It's constant and not increasing at variable with distance.
i.e. not increasing with distance.

With a 50mm (~2 inch) objective.....1" off at 20 feet......1" off at 200 feet........1" off at 2,000 feet.

That's why it matters to a squirrel at 20 feet but not to a steel plate at 2,000 feet.

I read the article but didn't get that from it. But I also do not have enough information yet to argue your interpretation either.

 

[HKShooter65]

I was wrong.
Maximum parallax error is 1/2 the diameter of the "exit pupil"....the lens nearest your eyeball. I's wrongly said it was 1/2 the distal-big lens. So it's less than I thought.
It's still about 1/2 inch each way at ANY shooting distance.

From the new referenced article (below)

"To calculate the maximum parallax error, we must know how far the eyeball can move off the optical axis. The MAXIMUM distance that the eyeball can move off the optical axis, before losing the image, is determined by the optical system’s EXIT PUPIL."

maximum parallax error is the size of the exit pupil.
So......less than an inch each way.

No way parallax could be 10 inches at 1,000 meters, or 2 miles for that matter.

It's the same at 10 feet or 10 miles.
So, it's significance DECREASES with distance.
That is so very much different than the other shooting variables we deal with.


Here:
paragraph 4
http://rimfirebenchrest.com/articles/parallax.html

To rimfire shooters or air rifle shooters parallax is a big deal.
To hunters or long distance steel plate shooters, nah.

Common misconception though.

 

[HKShooter65]

For an easy self-demo try it with a red dot like an Eotech.
Move your head all around behind it.

Dot moves the SAME amount at 1 foot, 10 feet, 100 feet.
Easy to see.

 

[rushthezeppelin]

Hmmmm guy with Leupold seems to be saying the opposite, that the further off your reticle is from being in the same plane as your target image, the bigger the potential deviation of POA to POI.

 

[Dawico]

Hmmmm guy with Leupold seems to be saying the opposite, that the further off your reticle is from being in the same plane as your target image, the bigger the potential deviation of POA to POI.

This video matches my understanding of how parallax affects your POA at longer distances.

 

[HKShooter65]

We need an optical expert to weigh in.
I heard what he said and we now have conflicting information.

He's clearly knowledgeable. If he's right I'll realign my own understanding. Some of my printed sources would, therefore, be in error.

Thanks

 

[Dawico]

We need an optical expert to weigh in.
I heard what he said and we now have conflicting information.

He's clearly knowledgeable. If he's right I'll realign my own understanding. Some of my printed sources would, therefore, be in error.

Thanks

I do know that parallax becomes a bigger issue as distance increases. That is why it is a big concern in the long range shooting crowd.

After reading the article you posted I am still under the impression that it is an angular function. It refers to parallax in MOA percentages, and MOA is angular.