Article on Eye alignment with Aperture sights

[Justsomedude]

An interesting (albeit long and technical) about Aperture sights.
http://dougkerr.net/pumpkin/articles/Aperture_Sight.pdf

[ATM]

Very informative and well written. I always just called it "magic".

[oladcock]

Cool JSD.... I've been telling folks "don't fuss centering the front post in the rear apperture, just get that front sight where it belongs". Not from previous instruction, just from my own observation. Nice to see it confirmed through real science! ...O.L.

[Unbridled Liberty]

Wow.  Reading this document made me realize how dumb I am.  I would just summarize it by saying "Don't let perfect be the enemy of good enough.".

UL

[Spartan]

 I would like to see more about how he conducted his Live Fire 100 Yard experiment at the end.  To me it is hard to believe you can have the sights misaligned that far in differnet directions and have POI nearly the same as when the sights are alighned at 100 yards.  The results the author achieved in his experiment with himself shooting are in conflict with many major published works done on sight alighnment.

[ATM]

...To me it is hard to believe you can have the sights misaligned that far in differnet directions and have POI nearly the same as when the sights are alighned at 100 yards...

Seems to me that it is completely due to the parallax suppression effect. Moving the eye to the left a couple millimeters is the same as moving the still aligned rifle to the right a couple millimeters. The group should not change by more than those couple millimeters downrange.

With normal parallax, you would see an angular optical shift and you would re-aim and your POI would veer off by that same angle of error you just adjusted for ( and being an angle, that error would increase with distance).

However, with the parallax effect suppressed, the target image visually remains perched atop the sight when you move your eye (or the still aligned rifle in the opposite direction) so there is no need to re-aim and induce any angular error "correction" which we know has the effect of changing POI by MOA rather than an offset of millimeters.

Assuming that notch style irons do not suppress parallax in this manner at all, trying the experiment with both should provide very different results. I plan to compare the difference for myself on my next range trip.

[oladcock]

I would like to see more about how he conducted his Live Fire 100 Yard experiment at the end.  To me it is hard to believe you can have the sights misaligned that far in differnet directions and have POI nearly the same as when the sights are alighned at 100 yards.  The results the author achieved in his experiment with himself shooting are in conflict with many major published works done on sight alighnment.

I've done this "experiment" just not in the documented way he did. That's why I started stressing to not "fuss" the centering part. Another way of looking at it is lineing up objects through a TP tube, you can't be very far off and still "see" whatever it is (front post) you are lineing up. Your eye is a second TP tube, now if either "tube" is mis-aligned by like 1/2 the amount as with one, you can't see the front post. Just focus on that front post, ignore the app and shoot!....O.L.

[Justsomedude]

My 'experiment' happened shooting in a seated position Stage 2 on an AQT when I wasn't settled and didn't have good alignment.

I knew I was going to run out of time...it felt terrible but I could see the front sight/target and just went ahead and shot.
To my amazement, all the rounds were in the Black.

I still don't understand it (I fell asleep halfway through the article!) but it confirms my love of Aperture sights.

[Justin]

I would like to see more about how he conducted his Live Fire 100 Yard experiment at the end.  To me it is hard to believe you can have the sights misaligned that far in differnet directions and have POI nearly the same as when the sights are alighned at 100 yards.  The results the author achieved in his experiment with himself shooting are in conflict with many major published works done on sight alighnment.

Yes, I'm having a real hard time with this too. It could be that I'm just ignorant (very possible).

The article looks great in regards of how rays in lenses work. Here's what I'm struggling with though:

While I agree no matter how your head is turned in regards to your pupil and eye lense that it has near no effect, the rear sight aperature is not a lense.

I would like to believe it is "magic" but, my (possibly ignorant) logic is getting in the way. It really doesn't help that the author's groups suck. If he could fire with some consistency it would do a lot to make his case.

So lets assume you have proper sight alignment/picture. (Front sight is centered both vertically and horizontally in the rear sight aperture and is on the target)

So lets assume this will produce bullseye shots.

To change the sight alignment as described in the article you would do what? Move rear sight aperature (back of the rifle) to an incorrect sight alignment while keeping the front sight aligned with the target....

Once you've moved the back of the rifle, you've also moved the front (keeping the front sight on an axis and centered on the target). So, if someone could explain to me how keeping the front sight on the target, yet moving the muzzle in another direction can produce accurate shots, I'd appreciate it.

I can turn the rifle 90 degrees and still look at the front sight and line it up on the target, that doesn't mean I'm going to hit the target. It means I'm going to hit some poor schmuck on the line.

Or maybe I'm just ignorant.....

P.S. If this article is about not having to have your eye centered behind the aperture, I agree 100%.

[Justsomedude]

No...he is just saying that the CENTERING isn't as crucial as long as you are looking through the rear sight.
He's a clip from the article:

"Parallax shift--the reality
In actual practice, we find that if we look through an aperture sight, with the aim of the rifle fixed (perhaps it is held in a sighting vise), and move our eye from side to side, we see almost no change in the relative locations of the tip of the front sight and the target (what shooters call the "sight picture"). Essentially, the phenomenon of parallax shift does not appear.
On the other hand, if, as a "check" on our observations, we raise our eye so that we look completely over the rear sight, and adjust the pointing of the rifle so that again the tip of the front sight aligns with the target, we find that when we move our eye from side to side by the same amount we did before, we do see a definite shift in the relative locations of the tip of the front sight and the target. This is in fact parallax shift at work."

[Justin]

okay then, I'll no longer making the rear sight windage adjustments because it isn't crucial.

[Justsomedude]

 But that changes the alignment of the actual Front to Back sights.
I don't think that he is saying that doesn't matter.
He's talking about how your eye perceives it.

And NO, his groups weren't good to begin with.

I do high speed pistol shooting.
A big part of that is learning when you are getting "enough information to make the shot".  If you wait to get a tight mentally confirmed sight picture, you have already lost.
And lots of the guys that are good at that aren't great at Bullseye shooting.
But they Hit the "A" Zone FAST.

[ATM]

...To change the sight alignment as described in the article you would do what?

Move your eye. Leave the actual rifle alignment untouched.

P.S. If this article is about not having to have your eye centered behind the aperture, I agree 100%.

That's it in a nutshell.

[Nickle]

The article is, in my opinion, Junk Science. I'll stick with what I've learned the past 40 plus years.

Now, the eye will tend to naturally center the front sight in the rear aperture. The key is knowing that, then to quit fighting it. That gets you "close enough". By the way, that's what I teach, and I get results. (That is, the shooters get results.)

Small failures of sight alignment will not make all extremely gross target errors. Just doesn't happen. And, if your real issue of sight alignment is really caused by changed stock weld, then your sights could actually be properly aligned even though they appear to be off.

As to his experiment, I think he should have used a more accurate rifle, and definitely should've done more testing. 100 yards? Did he mention weather/wind conditions? Did they affect his results? More groups with a better rifle would've answered that.

[Mr Pete]

For Marksmanship purposes this article is irrelevant.  If a student lacks the focus to center the front sight then how do they call the shot or focus on the front sight?  How do you get that kind of focus?  Practice.  Mental and physical discipline are keys to consistency and repeatability.

1)  Instruction - The author may be correct about sloppy eye alignment but do Olympic shooters become Olympic shooters by being sloppy?  I'm certainly not going to teach people to be sloppy and not pay attention.

2)  Science - The aperture does function as a lens - light is changed/filtered, DOF is increased, etc.  Ever see those "glasses" that have nothing but pinholes on an opaque "lens"?  There may be science behind it but so what?  One factoid like this doesn't tell the whole story. 

3)  Data - I'm betting that different sized apertures will make a huge difference on how much of this effect is observed.  He tested with 1mm sights (.04").  A2 sights vary between (.08") small aperture and large (.25")...2 to 6 times larger than what he tested.  The author's single point of data doesn't prove his "observations" have anything to do with anything other than his test setup.  So, unless you have exactly the same setup, eyes, cheek weld, etc, you're betting his method works better than what has been taught and proven to work.

4)  Implications - His theory, while interesting, offers nothing of practical value.  I like his conclusion that people whose life depends on hitting what they aim at should adopt his method because of this totally incomplete experiment. 

My summary:  Interesting to know, doesn't make a bit of difference.

[ATM]

If it doesn't make a bit of difference, why do people bother adjusting the parallax on their scopes to the distance they're shooting?

If we always maintained the same perfectly repeatable cheekweld position, suppressing the parallax effect that magnifies minor imperfections in optical alignment would be unnecessary.

This study does nothing to undermine or counter the fundamentals we instruct, it simply explains why some sighting systems are more forgiving of the imperfect.

I fail to grasp how understanding and accepting that bit of information would constitute promoting sloppiness. 

[Mr Pete]

This study does nothing to undermine or counter the fundamentals we instruct, it simply explains why some sighting systems are more forgiving of the imperfect.

Actually that is the biggest issue I have with his paper...

Shooters have many things to concern themselves with during the
execution of a shot. These include aiming, maintaining a natural point
of aim, trigger technique, breathing, and wind estimation. By removing
an item from the work load on the shooter's list (and removing what is
sometimes erroneously identified as a source of off-shot calls), the
available time can be better spent concentrating on the tasks that
make a difference.

The above quote comes from a section titled, "The Practical Benefit".  The implications of his experiment are:
1)  Eye position doesn't matter
2)  Remove eye position from the equation (as referenced in the above quote)

I understand and respect the author.  I believe he is actually correct (within the parameters of his experiment).  It is his, "Practical Benefit", that I take issue with.  Pretend the author is correct in all ways, what am I going to do with that information?  What do you teach students?

I think that if we removed (as he suggested) eye position from the fundamentals it would not be giving students adequate direction (which has other benefits).  We don't just say, "lay down for prone".  We shouldn't say, "front post just anywhere in the peep, it doesn't matter".  I said sloppiness because by ignoring "sight alignment" it is a lack of care or precision. 

The paper is great.  It tells us that peep sights are genius and that they have some inherent forgiveness built in!  Will I change the way I teach or my emphasis on sight alignment (which is only about 30 seconds over a weekend)?  I choose not to implement the suggestions of the author though I have learned from him.

-Peter

[Justsomedude]

I'm not going to change what I DO because of the article...
I think it addresses the concept of "your eye will naturally align with the Aperture" though.