24hourcampfire.com
24hourcampfire.com
Previous Thread
Next Thread
Print Thread
Hop To
Page 1 of 2 1 2
Joined: Jul 2009
Posts: 905
T
tcp Offline OP
Campfire Regular
OP Offline
Campfire Regular
T
Joined: Jul 2009
Posts: 905
For scopes with non adjustable parallax, most factories set these at 100 or 150 yards, likely as that is the distance most of those scopes are used at primarily.

However, if one was going to shoot regularly at 400-500 yards, what would be the downside to having parallax set at 200-250 yards so that longer range parallax errors were reduced? What degree of increased error would be seen at 100 yards set up this way?

Thank you


If you can't be a good example, may you at least serve as a dreadful warning
BP-B2

Joined: Dec 2014
Posts: 8,969
F
Campfire Outfitter
Offline
Campfire Outfitter
F
Joined: Dec 2014
Posts: 8,969
Barsness wrote about this, he basically said if you are seeing parallax shift on your target, on a non adjustable scope...move your eye to the rear past normal eye relief, until the image shrinks with a big black donut around the periphery, and your parallax will be reduced or eliminated. It certainly works for me. You plan on shooting "regularly" at 400 or 500...which, on most adjustable scopes I've seen, those ranges are in the 'infinity' range. An example of one is not much, but I sent a fixed parallax low price Bushnell 3200 and some money in to have them adjust parallax to 50 meters, it came back worse than it was originally. And, owning several mid market scopes with parallax adjustments, sitting on the same bench eyeing the target at the same distance, seldom do any of them match the yardages printed on the adjustment ring...I have often wondered if the diopter/focus adjustment affects the parallax settings. I have done a lot of reading on optics and the mathematical rules that dictate their limitations...and understand nothing.


Well this is a fine pickle we're in, should'a listened to Joe McCarthy and George Orwell I guess.
Joined: Jul 2009
Posts: 905
T
tcp Offline OP
Campfire Regular
OP Offline
Campfire Regular
T
Joined: Jul 2009
Posts: 905
Thank you for the reply, I do know how to reduce parallax error by moving my head back and centering the image.

My question was more specifically what degree of error is introduced at 100 yards if parallax is adjusted to 250? and then how much improvement in parallax error does this result in at 500 yards? More simply, if one is going to shoot with equal frequency at 100 yards and 500 yards is the ideal place to set parallax 250 yards in order to minimize error at both the near and far range?

For the sake of accuracy in the above example- the scope would be a 1"tube 3.5-10x with 40mm objective

Thank you


If you can't be a good example, may you at least serve as a dreadful warning
Joined: Jul 2001
Posts: 59,910
M
Campfire Kahuna
Offline
Campfire Kahuna
M
Joined: Jul 2001
Posts: 59,910
Such a set-up won't result in a lot of parallax at 100-150 or 400-500 yards, but it will be there.

Exactly how much depends on the magnification and objective lens diameter--and what size target you're intending to shoot.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Joined: Dec 2014
Posts: 8,969
F
Campfire Outfitter
Offline
Campfire Outfitter
F
Joined: Dec 2014
Posts: 8,969
Note how artfully I dodged the actual question.
I wonder if...let's say your scope is factory set for no parallax at 100, you set up targets at 100, 250 and 500, you do the head wobble at all 3 targets recording your estimation of parallax shift in moa or whatever. F'rinstance, let's say you estimate zero shift @ 100, 1 moa @ 250 and 2 moa @ 500. OK, then you get your scope tuned to have zero shift at 250...could you then interpolate that at 100 you will have 1 moa possible error and then at 500 you will have 1 moa possible error? My guess is no, it doesn't look like a uniform numerical progression when you look at the yardage marks on an adjustable parallax objective bell. But, more confusing, is that just a function of an incompatible number of threads per inch on the adjustment? Oh, my head hurts, I'm going to have a beer. Ask Mathman.


Well this is a fine pickle we're in, should'a listened to Joe McCarthy and George Orwell I guess.
IC B2

Joined: Nov 2006
Posts: 3,640
B
Campfire Tracker
Offline
Campfire Tracker
B
Joined: Nov 2006
Posts: 3,640
I am the wrong person to answer your question properly.....................but.


There is always a degree of error with parallax, if in theory you have your parallax set at 250 yards it is really not at 250 yards all the time, weather conditions and other factors can change parallax quite a bit.

A couple ways to manage parallax, turn down your power or have a scope with parallax adjustment.

I bought a Leupold VX-3i 4.5-14X40 a couple years ago, the model 170691 that has no parallax adjustment.....
it always has parallax issues above 10X no matter the range (btw: I Hate this scope !!!!)
I then bought the same scope with parallax adjustment model 170699 and it is fantastic.

Trying to guess where to have a fixed parallax set is futile, either lower the power or buy a scope with adjustable parallax.

Joined: Jul 2001
Posts: 59,910
M
Campfire Kahuna
Offline
Campfire Kahuna
M
Joined: Jul 2001
Posts: 59,910
Originally Posted by boatanchor

There is always a degree of error with parallax, if in theory you have your parallax set at 250 yards it is really not at 250 yards all the time, weather conditions and other factors can change parallax quite a bit.


Yep, air density can change quite a bit from day to day--which is why I check apparent parallax every time I test-fire rifles at the range. There are other reasons as well, but that's one few shooters understand.

But magnification REALLY accentuates parallax problems. The absolute worst parallax I've seen in any higher-grade factory scope was in a 5-15x Zeiss almost 20 years ago. This was a new model, apparently made primarily for the American market, with NO parallax adjustment of any sort.

It was on a custom .22-250 I'd been invited to try on a prairie dog shoot. The rifle shot very well during sight-in at 100 yards, but in the field, on any shot beyond about 250 yards (where I generally had it on 15x) it had me talking to myself. Finally checked the parallax at 400 yards, and found it was 12-15 inches.... Apparently Zeiss decided to go back to the drawing board on that one, because I never saw it in any catalog.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Joined: Jul 2012
Posts: 2,565
D
Campfire Regular
Offline
Campfire Regular
D
Joined: Jul 2012
Posts: 2,565
The maximum error, ie that where your eye is located right at the edge of the exit pupil, can be calculated:

Maximum error = 0.5 (d)abs(t-p)/p

where d is objective lens diameter, t is target distance, and p is parallax-free distance. If d is denominated in mm, so will the error be in mm.

So, for example, if we take the op's question, and insert some numbers, let's say that the scope is set to be parallax free at 250 yards, and it has a 40 mm objective lens. At 100 yards, the maximum error would be 12 mm. At 500 yards it would be 20 mm.

If on the other hand our scope was set to be parallax free at 150 yards, maximum error at 500 would be 46 2/3 mm. This is less than 0.4 moa. That is with the eye displaced as far as it can be from the axis of the scope without losing the image.

You can also calculate error for a given displacement from the scope axis x if you also plug in magnification m, as follows:


Error = (xm)abs(t-p)/(p), provided that x < 1/2 exit pupil diameter

So, for example, with a scope set to be parallax free at 150, shooting at 500 yards, and where your eye is, say, 1 mm from the scope axis at the eye-relief distance, you can calculate for a 3x magnification:

Error= 1x3 abs((500-150)/150) = 7 mm

While at 15 x

Error=1x15 abs((500-150)/150) = 35 mm

Joined: Apr 2017
Posts: 134
M
Campfire Member
Offline
Campfire Member
M
Joined: Apr 2017
Posts: 134
I was checking 3 rifles this weekend for hunting season here in Colorado
Mine and my two kids rifles

I have a 100y target & 400y

My scope had parallax adjustment, I went right for the 400y target, 2” group, couple clicks adjustment, good to go

The kids rifles have cheap scopes, their rifles shot just over one inch groups at 100y, could not find the 400y target (2ftx4ft) after a dozen shots, Maybe a bullet on the corner here and there. Gave up, going to tell them 200y max

I blame the parallax.... their rifles have a super short LOP so hard to do the hold your head back trick

Joined: Jul 2009
Posts: 905
T
tcp Offline OP
Campfire Regular
OP Offline
Campfire Regular
T
Joined: Jul 2009
Posts: 905
Originally Posted by dan_oz
The maximum error, ie that where your eye is located right at the edge of the exit pupil, can be calculated:

Maximum error = 0.5 (d)abs(t-p)/p

where d is objective lens diameter, t is target distance, and p is parallax-free distance. If d is denominated in mm, so will the error be in mm.

So, for example, if we take the op's question, and insert some numbers, let's say that the scope is set to be parallax free at 250 yards, and it has a 40 mm objective lens. At 100 yards, the maximum error would be 12 mm. At 500 yards it would be 20 mm.

If on the other hand our scope was set to be parallax free at 150 yards, maximum error at 500 would be 46 2/3 mm. This is less than 0.4 moa. That is with the eye displaced as far as it can be from the axis of the scope without losing the image.

You can also calculate error for a given displacement from the scope axis x if you also plug in magnification m, as follows:


Error = (xm)abs(t-p)/(p), provided that x < 1/2 exit pupil diameter

So, for example, with a scope set to be parallax free at 150, shooting at 500 yards, and where your eye is, say, 1 mm from the scope axis at the eye-relief distance, you can calculate for a 3x magnification:

Error= 1x3 abs((500-150)/150) = 7 mm

While at 15 x

Error=1x15 abs((500-150)/150) = 35 mm



Dan- I appreciate your detailed reply.

In the above example. If maximum parallax error at 500 yards is calculated at 46.6mm is that independent of magnification? Thus would a 10 power scope in that example multiply that 46.6mm error?

Thank you.


If you can't be a good example, may you at least serve as a dreadful warning
IC B3

Joined: Jul 2012
Posts: 2,565
D
Campfire Regular
Offline
Campfire Regular
D
Joined: Jul 2012
Posts: 2,565
Originally Posted by tcp
Originally Posted by dan_oz
The maximum error, ie that where your eye is located right at the edge of the exit pupil, can be calculated:

Maximum error = 0.5 (d)abs(t-p)/p

where d is objective lens diameter, t is target distance, and p is parallax-free distance. If d is denominated in mm, so will the error be in mm.

So, for example, if we take the op's question, and insert some numbers, let's say that the scope is set to be parallax free at 250 yards, and it has a 40 mm objective lens. At 100 yards, the maximum error would be 12 mm. At 500 yards it would be 20 mm.

If on the other hand our scope was set to be parallax free at 150 yards, maximum error at 500 would be 46 2/3 mm. This is less than 0.4 moa. That is with the eye displaced as far as it can be from the axis of the scope without losing the image.

You can also calculate error for a given displacement from the scope axis x if you also plug in magnification m, as follows:


Error = (xm)abs(t-p)/(p), provided that x < 1/2 exit pupil diameter

So, for example, with a scope set to be parallax free at 150, shooting at 500 yards, and where your eye is, say, 1 mm from the scope axis at the eye-relief distance, you can calculate for a 3x magnification:

Error= 1x3 abs((500-150)/150) = 7 mm

While at 15 x

Error=1x15 abs((500-150)/150) = 35 mm



Dan- I appreciate your detailed reply.

In the above example. If maximum parallax error at 500 yards is calculated at 46.6mm is that independent of magnification? Thus would a 10 power scope in that example multiply that 46.6mm error?

Thank you.


For smaller errors in eye placement, parallax error is directly proportional to magnification, provided that the error will be less than the maximum.

The maximum error is independent of magnification. Bear in mind though that this represents a situation where your eye is as off-axis as it can be while still being able to see the image.

Joined: Dec 2014
Posts: 8,969
F
Campfire Outfitter
Offline
Campfire Outfitter
F
Joined: Dec 2014
Posts: 8,969
I used to think the OZ cousins were just average guys..but upon some reflection, I am convinced that being upside down your whole life, stimulates the brain with increased blood flow...I'm sure of it, evidenced by the above posts.


Well this is a fine pickle we're in, should'a listened to Joe McCarthy and George Orwell I guess.
Joined: Nov 2005
Posts: 22,989
G
Campfire Ranger
Online Content
Campfire Ranger
G
Joined: Nov 2005
Posts: 22,989
Originally Posted by flintlocke
I used to think the OZ cousins were just average guys..but upon some reflection, I am convinced that being upside down your whole life, stimulates the brain with increased blood flow...I'm sure of it, evidenced by the above posts.



👍👍


"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty
Joined: Jul 2001
Posts: 59,910
M
Campfire Kahuna
Offline
Campfire Kahuna
M
Joined: Jul 2001
Posts: 59,910
The parallax formula is not a Down Under secret. I first encountered it during a visit to the Leupold factory years ago, but that was back when their tech and PR guys were more technically oriented.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Joined: Jan 2010
Posts: 32,129
Campfire 'Bwana
Offline
Campfire 'Bwana
Joined: Jan 2010
Posts: 32,129
Originally Posted by Mule Deer
I first encountered it during a visit to the Leupold factory years ago, but that was back when their tech and PR guys were more technically oriented.



LOL


Originally Posted by 16penny
If you put Taco Bell sauce in your ramen noodles it tastes just like poverty
Joined: Nov 2013
Posts: 28,526
Campfire Ranger
Offline
Campfire Ranger
Joined: Nov 2013
Posts: 28,526
Originally Posted by Mule Deer
The parallax formula is not a Down Under secret. I first encountered it during a visit to the Leupold factory years ago, but that was back when their tech and PR guys were more technically oriented.


As opposed to being shucking and jiving experts?

I think I’m about through with any scope over 10x. That seems to be the place where they get iffy with eye-relief, eyebox etc. maybe I need to spend more money on them….


What fresh Hell is this?
Joined: Feb 2002
Posts: 4,302
Campfire Tracker
Offline
Campfire Tracker
Joined: Feb 2002
Posts: 4,302
Another part of dealing with parallax is keeping your head in the same place between shots. I have made a lot of cash betting folks. Here is how the bet goes:
5 tries....only have to be in the exact same place twice. I lay down $500 in cash.
I put one of my rifles in a large vise, tightened down where it cant move. Set up two dial indicators on magnetic bases. Get the shooter on the rifle. Take a Sharpie, mark two places on the side of their head. Move the indicators to those marks and zero. Shooter gets off the rifle, then back on 5 times. I give as much time between as wanted. Shooter then looks at the entire video to see he was not scammed. Then pays me $500. I haven't lost this bet yet. I haven't had a shooter yet that can get back on both marks, let alone to zero.
We aren't nearly as good at this as we think.
Charlie

P.S...the bet is good for anyone with some extra cash. Or some gun stuff.


The data and opinions contained in these posts are the results of experiences with my equipment. NO CONCLUSIONS SHOULD BE DRAWN FROM ANY DATA PRESENTED, DO NOT, UNDER ANY CIRCUMSTANCES, ATTEMPT TO REPLICATE THESE RESULTSj
Joined: Jul 2001
Posts: 59,910
M
Campfire Kahuna
Offline
Campfire Kahuna
M
Joined: Jul 2001
Posts: 59,910
Originally Posted by Pappy348
I think I’m about through with any scope over 10x. That seems to be the place where they get iffy with eye-relief, eyebox etc. maybe I need to spend more money on them….


That's exactly why most (but not all) scopes above 10x have some sort of parallax adjustment.

It's also partly why the 5-15x Zeiss I mentioned earlier in this thread had so much parallax on 10x. The other reason was its big objective lens, which as I recall was around 50mm.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Joined: Dec 2012
Posts: 4,841
R
Campfire Tracker
Offline
Campfire Tracker
R
Joined: Dec 2012
Posts: 4,841
Originally Posted by Charlie_Sisk
Another part of dealing with parallax is keeping your head in the same place between shots. I have made a lot of cash betting folks. Here is how the bet goes:
5 tries....only have to be in the exact same place twice. I lay down $500 in cash.
I put one of my rifles in a large vise, tightened down where it cant move. Set up two dial indicators on magnetic bases. Get the shooter on the rifle. Take a Sharpie, mark two places on the side of their head. Move the indicators to those marks and zero. Shooter gets off the rifle, then back on 5 times. I give as much time between as wanted. Shooter then looks at the entire video to see he was not scammed. Then pays me $500. I haven't lost this bet yet. I haven't had a shooter yet that can get back on both marks, let alone to zero.
We aren't nearly as good at this as we think.
Charlie

P.S...the bet is good for anyone with some extra cash. Or some gun stuff.


I'm curious: how much difference in group size does it make at 100 yards? If the question makes any sense.


"An archer sees how far he can be from a target and still hit it, a bowhunter sees how close he can get before he shoots." It is certainly easy to use that same line of thinking with firearms. -- Unknown
Joined: Jun 2004
Posts: 44,710
M
Campfire 'Bwana
Offline
Campfire 'Bwana
M
Joined: Jun 2004
Posts: 44,710
That will depend on the parallax being dialed out or not at 100 yards.

Page 1 of 2 1 2

Moderated by  RickBin 

Link Copied to Clipboard
YB23

Who's Online Now
404 members (007FJ, 1lesfox, 1lessdog, 06hunter59, 01Foreman400, 10Glocks, 38 invisible), 2,363 guests, and 976 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums81
Topics1,187,731
Posts18,400,902
Members73,822
Most Online11,491
Jul 7th, 2023


 







Fish & Game Departments | Solunar Tables | Mission Statement | Privacy Policy | Contact Us | DMCA
Hunting | Fishing | Camping | Backpacking | Reloading | Campfire Forums | Gear Shop
Copyright © 2000-2024 24hourcampfire.com, Inc. All Rights Reserved.
Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.3.33 Page Time: 0.103s Queries: 15 (0.006s) Memory: 0.9045 MB (Peak: 1.0853 MB) Data Comp: Zlib Server Time: 2024-03-29 11:57:58 UTC
Valid HTML 5 and Valid CSS