TargetTalk

I made an interesting discovery after noticing that my scores in open\iron sight were significantly lower than my scoped prone scores. After decades of never having an eye exam I discovered that I am now far sighted and in need of glasses. Mostly due to age and needing correction magnification for reading. I was prescribed with glasses with slight magnification. So my question is what are the NRA and issf rules regarding corrective lenses and magnification? I noticed a distinct difference with the new glasses on the front sight but the target is still somewhat distorted. Any advise for dealing with older eyes in the shooting sports would be greatly appreciated.

ISSF rules allow a corrective lens worn in glasses or attached to the rearsight.

No one can see the target and the front sight both in focus at the same time. Younger shooters have the ability to "accommodate" (rapid refocusing between two objects) which the brain can interpret as both being in focus. Unfortunately, as we age, accommodation becomes much slower. Having a sharply focused front sight, with slightly blurred target is the accepted norm for us.

Thank you both for the replies. I am thinking that this may be something I took for granted when I was younger and never really gave it much thought. Now I need to find someone to make a corrective lens for my shooting glasses as my local optometrist will not.

Tim S wrote: ↑Sun Mar 10, 2019 1:50 pm ISSF rules allow a corrective lens worn in glasses or attached to the rearsight.

Does that apply to something like the Centra Hawk?

I wear a corrective lens in a Champion frame for 10m AP but having a lens in the rear sight of my KK300 would be more convenient than I think for rifle. I'm currently not using any correction for SB but probably should.

greentangerine wrote: ↑Mon Mar 11, 2019 6:32 pm Does that apply to something like the Centra Hawk?

I wear a corrective lens in a Champion frame for 10m AP but having a lens in the rear sight of my KK300 would be more convenient than I think for rifle. I'm currently not using any correction for SB but probably should.

No, I believe this would not be permitted. An adjustable focus lens has two lenses inside to work. As a side effect it also magnifies, at all +/- dioptre settings.

Lens holders are permitted, like these: https://www.intershoot.co.uk/acatalog/Lens-Holders.html You have to get the lens separately from an optician, as you do with spectacle frames.

I noticed a distinct difference with the new glasses on the front sight but the target is still somewhat distorted. Any advise for dealing with older eyes in the shooting sports would be greatly appreciated.

Seems that typically the distance prescription for everyday glasses does not work well for iron sight shooting. Hence the need for dedicated shooting glasses.

Art Neergard of Shooting Sight Inc recommends adding (+) 0.5 diopter to your distance correction. This is intended to achieve a clear image on the front sight element and still have a fairly sharp image of the bull. I believe Art sells a selection of lenses you can try in order to select the proper correction.

https://shootingsight.com/

Neal Stepp of International Shooting Services will provide a lens set for you to try as well.

http://www.iss-internationalshootersservice.com/

Both Neergard and Stepp are knowledgeable regarding vision and shooting and will procure a shooting lens for your frames.

Looking thru a corrective lens diagonally can cause problems. Hence there are eyeglass frames such as Knobloch, Champions and other which are adjustable. Bob Jones sells eyeglass frames which can be bent so the aiming eye lens can be centered in front of the eye while aiming.

Bob Jones sells eyeglass frames which are adjustable so the aiming eye lens can be centered in front of the eye.

http://www.bjonessights.com/glasses.html

I never had a problem with an eye doc providing a lens for shooting glasses.

Your eye has a focal range, called your depth of field. While a lens has only one theoretical focal point, there is a range of focus where the blur is smaller than your eye can resolve, so it appears in perfect focus, there is an even greater range where the blur is small enough that you can still use the image, and then there is the range where the blur is too great.

You can determine how big your depth of field is, as well as where the depth of field is centered, through the use of optics. The size of the depth of field is determined by the aperture size - either your pupil if you are shooting with just your eye, or a peep sight opening, or a merit disk that you stick on your glasses. Whichever is the smallest opening in your optical path is it. So for a peep to work, it has to be smaller than your pupil. The smaller the aperture, the larger your depth of field. This is why pin-hole cameras work; there comes a point where the aperture is so small that the depth of field is so big that it does not matter even matter that you don't have a lens.

Where the depth of field is centered is driven by the focal point of your eye. If you focus on the target, your depth of field will be from somewhere behind the target to somewhere in front of the target, but not far enough in front of the target that your sight is in focus. If you focus on the front sight, your depth of field will go from somewhere closer than your sight, to somewhere beyond your sight, but not far enough in front of the sight that the target is also in focus. However, if you focus BETWEEN the sight and the target at some magical point in space, your depth of field will go from some point closer than the magic point to somewhere beyond the magic point, and if your depth of field is big enough, there is actually a possibility that both the sight and the target are in reasonable focus at the same time. There is a lot of math that goes in calculating the magic point, but photographers have done it, and it is referred to as the hyperfocal distance. Of course, when we were young, we didn't need the optical math, our brain just made our eye focus at the hyperfocal point by trying to get the clearest picture.

So: where do you want to focus? For rifle with an aperture sight it is pretty obvious that you want to balance your focus between the front sight and the target. The peep will never be in focus. Pistol is a little more tricky. The rear sight is further from you, so you CAN see it. However, the sights being so close together, sight alignment is more critical than sight/target alignment, so many shooters prefer to bias their focus a little closer to the sights than the target.

Someone mentioned accommodation - this is your eye's ability to change focus. Your relaxed eye is elastic, and will focus at infinity. You exert the ciliary muscle in your eye to squeeze the lens and pull your focus in close. As we get older, the lens loses its flexibility and you have to exert the muscle a LOT to pull in your focus; sometimes you can't even do it at all. Luckily, by adding positive diopter lenses in front of your eye (aka cheaters), the lens will artificially shift your focal point closer, so your eye does not have to make the effort. For reading, the correct power is about 2.00 diopters, but this puts your focal point at arm's length, MUCH closer than your desired hyperfocal distance. For anyone who has ever tried sighting with reading glasses on, they will know that your sights are sharp as can be, but the target is much too blurry. So the real trick is to determine where your hyperfocal distance lies, and calculate the lens power needed so your eye's relaxed focal point falls at the hyperfocal distance, and you get the sight picture you want while your eye muscle stays relaxed. This way you can shoot without your eye muscle getting tired, so eye strain sets in, and your sight picture does not drift over the course of a match.

I won't go through the actual math here, but bottom line is that for a rifle, you typically want to add +0.50 diopters to your distance vision prescription (if any - otherwise just use +0.50 diopters). For a pistol, to get your focus a little closer to bias it on seeing the sight alignment, the number works out to adding +0.75. There are several ways to do this, glasses, lenses inserted into the sights, contacts ... each has their own merit, based on how much distance correction you need.

Several disclaimers: everyone's eyes are slightly different, and indeed your vision can change during the day (esp if you are diabetic), so these numbers are excellent starting points, and I'd say they apply to about 90% of the people. Some might want a little higher or a little lower. Obviously, personal preference also plays in to this. Also, I do not recommend shooting with progressive lenses, You can tip your head to get the perfect sight picture, but you cannot tip your head exactly the same every shot, so there is some drift in consistency.

Finally, I'm not a doctor, I'm an engineer who studied optics, so this is not medical advice. I recommend that any playing around with lens powers ought to start with a visit to a real doctor to get a base line vision check, and then this math can be applied to modify that prescription.

I understand the ISSF wants to ban eyeglasses and have all lenses on the rear sight.
A few companies are now making a sight lens holder.

MGoodman wrote: ↑Sat Apr 06, 2019 9:29 pm I understand the ISSF wants to ban eyeglasses and have all lenses on the rear sight.
A few companies are now making a sight lens holder.

??? Do you have a source for this? The ISSF only allowed lens holders on rifles in 2017, after many years of a strict glasses only policy. This would be a bit of a U-turn.

Wow, that makes NO sense. Will they ban contacts as well?

Some people are blind as a bat, so if you insist on lenses on the gun only, they can aim, but after they take the shot and go to write in their log book, or adjust the sights, they can't do it without putting glasses on between shots.

If this is true, I'd suggest what the ISSF really needs, is someone who knows their optics on the rules committee. When you write a rule without knowing what you are talking about, people who DO know what they are talking about will twist the rule to their advantage. This is what happened with match rifles, where the rule was that you could have one lens, so people figured out that if you put one lens in the front sight, you got a magnification benefit. This is how the adjustable focus apertures, which use two lenses to create a small Gallilean telescope got developed. Adjustable focus is a noble thing to do, but a by-product is that you also get a 1.5x magnification.

Here is another option to help you see the target when using iron sights.

www.SeeBetterShootBetter.com

kwc1059 wrote: ↑Thu Jun 20, 2019 5:28 pm Here is another option to help you see the target when using iron sights.

www.SeeBetterShootBetter.com

I think he's already using aperture sights, so this won't help.