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Old March 10, 2018, 11:24 AM   #38
COSteve
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Join Date: September 6, 2009
Posts: 1,344
Quote:
Originally Posted by JeepHammer View Post
Just a little bit of trivia,
A trip to the eye doctor told the tale, my eyes had flattened and I'd lost the ability to focus in three planes, couldn't see the rear sight, front sight & Target at the same time. My prescription changed 4 times in one year. Crap on a cracker!

Interestingly enough, without my glasses, and with a small aperture I could shoot without glasses. For some reason, looking through that little hole clears the sight picture up. I can't see crap without my glasses unless it's through a aperture sight, which makes no sense at all to me, but it does work.
I suspect that you're far sighted as that condition generally makes itself apparent in one's early 40s. I am far sighted as well and at 70, I'm also 'blessed' with astigmatism in both eyes. I, however, still do most of my shooting with iron sights by using some optical principles I learned over the years and I'm still able to clearly see both my front sight and the target.

How? By understanding and using basic Optical principles to my benefit. Let's look at your 'interesting discovery' for a minute and you'll understand what I mean. It turns out that your small aperture is expanding your Depth of Field (DoF). Google 'Depth of Field' as you'll find it's a term most used in photography but the optical principle is of great benefit to us shooters as well.

In short, optically, the area in focus at a given setting is perceived as a zone rather than a plane. For example, when focusing on an object at 20ft, you might find that objects from 18-24ft are also in focus. It turns out that you can adjust the zone that is in focus by selecting the aperture size. This aperture must be close to the sensor / film / or your eye to affect the Depth of Field.

At a given lighting, the larger the aperture, the shorter the zone that is in focus and conversely, the smaller the aperture, the longer the zone. So, if one were to put, say a .042" diameter target aperture on a tang sight of one's rifle, snug up to the sight and sight through it, one would find that the Depth of Field was enormous. Like from nearer than your front sight to well past your target (even if it's 200yds away) so that everything within that field is clearly in focus.

Amazing!! Astounding!! Magic!! No, Optics.

That's why if you have a small aperture peep sight mounted on the rear of your receiver so you can get your eye close, ≈1" away, you can see your front sight and the target much better than just looking at both directly, DoF. However, if you're sighting through a larger aperture, like a normal size one on an AR, or the aperture is a few inches from your eye, the DoF is unchanged. Understanding optics, I use the principle of DoF to make a simple, free aid that allows me to keep using my semi-buckhorn sights and see the front sight and target clearly.

I simply take a piece of black electrical tape, a paper hole punch, and a small finishing nail and make a stick-on aperture for my shooting glasses. Punch out some 1/4" 'holes' from the electrical tape, take the finishing nail and put a small hole in the center of the tape circle, and stick them on the front of your shooting glasses where you sight through to shoot. The black tape circle seems to disappear as it's too close to your eye to focus on leaving a ghost like haze but the area in the center will magically appear to be sharp and clear. Sight through it and you'll magically see your sights and the target sharp and clear.

Here's an example of where to place the 'aperture' for a right handed shooter. You'll be amazed at the difference and it will cost you nothing to try it. Even though these are progress lens glasses and I'm looking through the 'distance' part, the small 'aperture' I've created near to my eye allows me to see the sights and my target clearly while not even noticing the black of the tape. Magic!!

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