How eye focus works for pistol shooters

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Post by visitor »

I believe cats have slit shaped pupils, because the prey they hunt lives in a world of grass and other growth that all has vertical edges, so they bias thei[r] focus to see vertical edges more.
There may be more than meets the eye.

A quick survey of related species shows that all of the big cats have round pupils including lion and cheetah which are grassland hunters. Timber rattlers who hunt in woods and grass have vertical slit pupils; eastern diamondbacks who hunt in woods and grass have round pupils; sidewinders who earn their living in the most arid parts of the desert southwest might be expected to have horizontal slit pupils. Sorry, their pupils are vertical.

I don't know the significance of these facts except that they complicate what was beginning to look like a simple proposition.
-luftskytter

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Post by -luftskytter »

Maybe it's just evolution?
I would imagine that such things may appear by coincidenceand for unknown reasons. This would then be the "raw material" that natural selection could use for picking the "surviving fittest".
So maybe horizontal pupils were not among the available choices in the gene pool when sidewinders were "developed"?

But come to think of it, maybe the only vertical lines in the world of sidewinders were edible prey? This would mean that horizontal lines are not very interesting for a sidewinder even if they are all over the place.
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ShootingSight
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Post by ShootingSight »

I am not an evolutionary biologist, so I can't provide any sort of validated answers, though I'll gladly hypothesize ....

I imagine larger cats start getting sufficiently bigger than the grass that this no longer helps them.

Another fact is that goats have horizontal pupils, however a biologist friend of mine pointed out that they spend much of their lives grazing, so their head is inclined 90 degrees forward ... meaning their slits are vertical while in eating mode.

You can mimick this yourself, by squinting. Things get clearer if you squint in a certain range.
moigy
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Sights & lenses

Post by moigy »

I too, am an Engineer, and have worked on low light micro-cameras since the 1960's. One of my Master's degrees is in Statistics.My competition rifle shooting goes back to the mid 1950's, while still in Junior High School.

Two separate thoughts to bring to the table.

1. Why pistols have usually a rectangular front blade to target a circle seems strange. Since my first Wnchester 52C with a small aperture rear sight (Lyman), I coupled aRedfield aperture sight up fromt. I bought a connecting tube (no glass) which eliminated extraneous light. The result was almost like a red dot. The front sight circle permitted just a sliver of light between that front sight and the target. When the sliver was uniform all around, I was in the X zone of the 10. It seems to me the something of that sort mightbe preferable for pistols as well. What say you all?

2. It amazes me that many shooters use formuli for Standard Deviation and Variance (by definition the square of the Standard Deviation), as well as other parametric tests for guns, ammunition, etc. when their sample size is small. When a Normally Distributed activity (something that really needs to be proven by every experimenter) has sample sizes below 30 (some use samples of size 3,5 or 10), the Parametric Statistics need special formulas to be meaningful. The Standard Error becomes, often, larger than the apparent SD. To be really meaningful and accurate, we need to first PROVE that the activity is normally distributed. Then we must use sufficient sample size and appropriate statistical techniques to have valid outcomes. It isn't easy. Ponder it.
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ShootingSight
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Post by ShootingSight »

On your point #1, you are right on. This is why match rifles use iris front sights.

Your eye has two mechanisms to determine aim. First is how many pixels on your retina are illuminated. You have a pixel about every 1/2MOA to 1MOA on your retina, depending on person. THis is a relatively crude mechanism to judge gaps between the iris and the bull.

You also have the ability to resolve about 16 different levels of brightness, so as the white spece gets bigger/smaller by increments of partial minutes, your eye can still judge if the ring looks slightly brighter on one side than the other, therein lies your accuracy benefit by using an iris.

On your point #2, I spent time discussing my testing with a statistician, and we never resolved how to address it. I only had 3 shooters, so n=3 is certainly not statistically accurate. However since each shooter shot 20 shots for each test condition, you begin to build confidence in each of their groups. At least more confidence than for n=3.

In my case, I'm not sure it matters. No matter what you do, the method gets applied equally to both sides of the test, so the directional notion that one is better than the other remains .... you can only affect if the difference is significant. But here, you come back to the n=3, so it wasn't likely significant in the first place.
moigy
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Iris on sights and targets

Post by moigy »

On small bore rifle shooting, the NRA specified that only 1 shot per bull be fired. I can see where that reduced arguments with scoring.

Why is it that the National Pistol Matches require more than one shot per bull? I observed my first such match about 10 days ago and at least 5 shots were required per target bull. I do not understand!!!

The iris you sell seems to be placed on or is part of the safety glasses.

How is that superior to a red dot?

How would your system work for someone who has had lens replacement as a result of cataracts?

Would not an iris type system, front and back, modified for pistols produce potentially better scores? Has anyone tried it?
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Post by ShootingSight »

The iris that I sell (will be selling - because I have not updated the web site yet) is a small sticker that goes on the safety glasses. It has an opening smaller than the pupil of your eye, so it will improve your depth of field.

I thought a red dot addresses the depth of field issue by having the red dot appear to come from infinity, so it is addressing the same problem differerntly.

As to cateracts, it depends on what lens you had put in. An option is a fixed focus lens. You could chose between something that was fixed at infinity, and you still needed glasses for everything close up. Another popular option was a 48" fixed focus, which is like a +0.75 diopter lens. This actually works well for rifle shooters, as the hyperfocal distance for a rifle is around 48", so you might be all set. In any event, you can still use a mild lens to tweek your focal point from wherever the fixed lens is to where you want it for shooting.

There are also diffractive lenses that have multiple focal points that people are implanting today. I do not know how these types of lenses interact with small apertures.
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Re: Sights & lenses

Post by BenEnglishTX »

moigy wrote:1. Why pistols have usually a rectangular front blade to target a circle seems strange. Since my first Wnchester 52C with a small aperture rear sight (Lyman), I coupled aRedfield aperture sight up fromt. I bought a connecting tube (no glass) which eliminated extraneous light. The result was almost like a red dot. The front sight circle permitted just a sliver of light between that front sight and the target. When the sliver was uniform all around, I was in the X zone of the 10. It seems to me the something of that sort mightbe preferable for pistols as well. What say you all?
I say you're exactly right. However, tradition gets in the way.

Shooting under International Handgun Metallic Silhouette Association sanction has always allowed what they now call "peep-on-peep" sights, what I grew up calling "aperture" sights and what European silhouette shooters refer to as "diopter" sights. I've been using such sights on my Unlimited-class competition pistol since the 1970s. Over the years they have become quite popular in the various "stand up and hold the pistol out in front of you" classes, too.

In fact, I have on the desk in front of me as I write this a .45 auto with a frame-mounted Weaver rail to which I've attached two XS Sights "Low Weaver Backup" sights, one at each end. In use, I put the rear circle around the front circle around the target and I endeavour to make the hammer fall when it appears I'm close to a concentric arrangement. On a well-lit range and shooting at a round bull, it's the easiest-to-sight iron-sighted .45 auto I've ever owned.

As for your specific description of a sighting arrangement with a tube from front to back, "tube sights" are a known concept, too. I remember the NRA national meeting in San Antonio, Texas, back in the mid- to late-1970s. One of the exhibitors was a Japanese company making a one-piece tube sight for use in silhouette shooting. It never made it to market (and would have failed, anyway, since it didn't comport with the rules at the time). Other tube sights, however, have done quite well. Kings Gun Works in Texas built a large number of pistol tube sights over the years. I have one (currently disassembled) that my sister used for years in competition. Ultimately, it was a bit crude, bulky, and fragile so they are rarely seen these days. Back in the day, though, when they were set up correctly and mechanically sound, those were easy sights to shoot. U.S. Optics has also made such a thing to a much higher mechanical quality standard. Unfortunately, theirs was (like pretty much all their products) far too heavy and so shockingly expensive that it never made inroads into any competitive venue of which I'm aware.

On a related note, some manufacturers of sights for action-type pistol shooting games have attempted to market "ghost ring" rear sights for use with front posts. While the sights are great compromises, providing improved accuracy with only a small penalty in speed, they've not taken the world by storm. In the fast-moving sports to which they were marketed, any accuracy gains were of little benefit and giving up even a tiny bit of speed to get those gains was a fine way to lose. Since those games also frequently involve shooting to the middle of a large, blank target instead of at a well-defined bull, the sights are frequently a total mismatch to the job. Without something to aim at, apertures are a bad idea. In those venues, then, using some sort of circular rear sight is viewed as a quaint, ultimately unsuccessful experiment.

What ultimately puts the nails in the coffin for this concept, though, is that putting circles on top of pistols for sighting equipment is just too non-traditional to be considered acceptable by some people. The ISSF specifically forbids it, even though it looks like it would be a natural for the Mens 50M Pistol event. The IMSSU (which sanctions silhouette shooting in many places outside the USA) has banned their use in an increasing number of classes over the years. Basically, there's a strong prejudice against this sort of sighting arrangement by people who value tradition over hitting the target. These are the same sorts of folks who banned low bore lines in rapid-fire pistols the first time someone started making such a thing. For some folks, if the bore isn't above the hand, if the sights aren't a notch and a post, if it just doesn't *look* like the pistols our great-grandfathers used, it should be banned. Right now, those people write the rules for the big sanctioning bodies. The progressive sanctioning bodies that would be OK with the concept tend to just skip right over it and allow red dots and scopes, rendering apertures obsolete. Pistol silhouette shooting in the USA seems to be the only place where circumstances have come together to allow and encourage their use.

Without more and broader competitive venues to work out the kinks, aperture sights on pistols will remain a mostly-unexplored niche.
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