Hello
I think I need glasses for my shooting, of late I am having difficulty getting a clear image while aiming. I have an appointment to see about this in a couple of weeks. Could someone tell me at what distance should the glasses be optimised at for 10m shooting please
Thanks
Glasses for 10m
Moderators: pilkguns, Marcus, m1963, David Levene, Spencer
You need to be able to clearly see the foresight and any astigmatism should be corrected
It really is best that you see an optician who understands the requirements of shooting. Failing that you need an understanding one who will not be worried about you bringing a rifle with you! At the very least you should take your sights with you and a target so that the optician has an idea what they are dealing with.
You don't say whether or not you have glasses normal use. If you do then a prescription in the region +0.5 to 1.0 dioptres over your normal prescription would probably be OK. But this is very much a generalisation.
If you put your location in your profile than maybe someone will be able to recommend a knowledgeable practitioner.
Rutty
It really is best that you see an optician who understands the requirements of shooting. Failing that you need an understanding one who will not be worried about you bringing a rifle with you! At the very least you should take your sights with you and a target so that the optician has an idea what they are dealing with.
You don't say whether or not you have glasses normal use. If you do then a prescription in the region +0.5 to 1.0 dioptres over your normal prescription would probably be OK. But this is very much a generalisation.
If you put your location in your profile than maybe someone will be able to recommend a knowledgeable practitioner.
Rutty
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ShootingSight
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Actually, the math is quite simple. Normally, target distance can be ignored, but at 10m, it just barely begins to make a difference.
The trick is that you want to do a mathematical average of the lens you need to see the target, and the lens you need to see the rear sight. That is your hyperfocal distance.
So, aim your pistol, and have someone measure distance from your eye to the rear sight. It needs to be in meters, but if you measure in inches, just multiply inches by 0.0254 to get meters. Hypothetically, let's say it is 0.9 meters.
Lens diopters are the inverse of the focal length of a lens (in meters), so a 2 diopter lens will focus at 1/2 meters, a 3 diopter lens will focus at 1/3 meters.
To see the target at 10 meters, you need a 0.1 diopter lens. TO see your rear sight you need a 1/0.9 = 1.11 diopters.
So take the average of 0.1 diopters and 1.11 diopters, and the answer is 0.6 diopters. Obviously, you need to repeat this math. The 0.1 diopters for the target is correct for 10 meters, but the exact distance to your rear sight isn't.
If you wear distance glasses, even with an astigmatism correction, you want to add the +0.6 to the spherical value.
So if you are slightly nearsighted, with an astigmatism, your prescription might be -1.25 sphere, -0.50 cylinder. So adding +0.6 to the sphere makes you -0.65 sph, -0.50 cyl for your shooting glasses.
Lenses are usually available in 1/4 diopter steps, and docs normally test you to the closest 1/4 diopter because of that, however your eye can see a 1/8 diopter step, so I would request he test you to the nearest 1/8, then you add the +0.6. After that, you will need to round down to the nearest 1/4 diopter lens.
So, bottom line is that lens math is exact. Once you know your distance correction, it should be straight forward to do the math to calculate how much you shift your distance vision for shooting.
Art Neergaard
ShootingSight
www.shootingsight.com
513-702-4879
The trick is that you want to do a mathematical average of the lens you need to see the target, and the lens you need to see the rear sight. That is your hyperfocal distance.
So, aim your pistol, and have someone measure distance from your eye to the rear sight. It needs to be in meters, but if you measure in inches, just multiply inches by 0.0254 to get meters. Hypothetically, let's say it is 0.9 meters.
Lens diopters are the inverse of the focal length of a lens (in meters), so a 2 diopter lens will focus at 1/2 meters, a 3 diopter lens will focus at 1/3 meters.
To see the target at 10 meters, you need a 0.1 diopter lens. TO see your rear sight you need a 1/0.9 = 1.11 diopters.
So take the average of 0.1 diopters and 1.11 diopters, and the answer is 0.6 diopters. Obviously, you need to repeat this math. The 0.1 diopters for the target is correct for 10 meters, but the exact distance to your rear sight isn't.
If you wear distance glasses, even with an astigmatism correction, you want to add the +0.6 to the spherical value.
So if you are slightly nearsighted, with an astigmatism, your prescription might be -1.25 sphere, -0.50 cylinder. So adding +0.6 to the sphere makes you -0.65 sph, -0.50 cyl for your shooting glasses.
Lenses are usually available in 1/4 diopter steps, and docs normally test you to the closest 1/4 diopter because of that, however your eye can see a 1/8 diopter step, so I would request he test you to the nearest 1/8, then you add the +0.6. After that, you will need to round down to the nearest 1/4 diopter lens.
So, bottom line is that lens math is exact. Once you know your distance correction, it should be straight forward to do the math to calculate how much you shift your distance vision for shooting.
Art Neergaard
ShootingSight
www.shootingsight.com
513-702-4879
Thanks for the replies, very helpful
I live in Anglesey North Wales, not many target shooters up here, I'd be very surprised to find a target shooting/understanding optician within 100 miles but if you know of one I'd me more than grateful. Yes I wear reading glasses and lately my old reading glasses have become ideal do drive in hence the visit to the optician in a couple of weeks and I'll certainly take along my sights and a target when I go. I don't shoot competitively anymore just in the garden but I do still take it very seriously.
Are these lenses available over the counter or are they optician supplied. Seeing as it looks like I need a distance prescription adding 0.6 to that would seem simple enough if the can be had from a target supplier
Most definitely a riffle (Anschutz 8002 S2)
I live in Anglesey North Wales, not many target shooters up here, I'd be very surprised to find a target shooting/understanding optician within 100 miles but if you know of one I'd me more than grateful. Yes I wear reading glasses and lately my old reading glasses have become ideal do drive in hence the visit to the optician in a couple of weeks and I'll certainly take along my sights and a target when I go. I don't shoot competitively anymore just in the garden but I do still take it very seriously.
Are these lenses available over the counter or are they optician supplied. Seeing as it looks like I need a distance prescription adding 0.6 to that would seem simple enough if the can be had from a target supplier
Most definitely a riffle (Anschutz 8002 S2)
1/ do you have shooting frames (knoblok, champion, etc.)? If so take them with youcolinlp wrote:...visit to the optician in a couple of weeks and I'll certainly take along my sights and a target when I go...
2/ I would take Shootingsight's recommendations/opinion with a grain of salt - find a rifle coach and get some advice (even if this means putting off the visit)
Colin
Its not quite as simple as people believe, yes there are formula's and guidance, with rifle its also uses the principle of the rear iris to get the compromise focus, the expert I use says its simple, set your lens to focus as 2 mts. That gives you a sharp focus on the foresight and the iris pulls in the long vision enough to get a comprimise on the long and the aiming mark, that works out at long vision plus 0.5 a diopter.
But, there is then the effect of astigmatism and the lazy eye muscle to consider, so he says it simple, then why did I travel a 4 hr around trip to get mine done exactly for me when two other opticians did not get it just right?
He's a long way from you but Stephen Hing in Shefford, near Bedford, is an expert in shooting lens's, he's been doing them for 30 years, he has some very high tech kit, and he can make the lens he prescribes while you wait.
Good Shooting
Robin
Note, first type was wrong! its plus 0.5 diopter on long, but still see an expert first!!!
Its not quite as simple as people believe, yes there are formula's and guidance, with rifle its also uses the principle of the rear iris to get the compromise focus, the expert I use says its simple, set your lens to focus as 2 mts. That gives you a sharp focus on the foresight and the iris pulls in the long vision enough to get a comprimise on the long and the aiming mark, that works out at long vision plus 0.5 a diopter.
But, there is then the effect of astigmatism and the lazy eye muscle to consider, so he says it simple, then why did I travel a 4 hr around trip to get mine done exactly for me when two other opticians did not get it just right?
He's a long way from you but Stephen Hing in Shefford, near Bedford, is an expert in shooting lens's, he's been doing them for 30 years, he has some very high tech kit, and he can make the lens he prescribes while you wait.
Good Shooting
Robin
Note, first type was wrong! its plus 0.5 diopter on long, but still see an expert first!!!
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ShootingSight
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Sorry, I got to the thread through the new post section, so didn't realize it is rifle.
If it is rifle, substitute the front sight distance from your eye. I usually shoot high power, where most match rifles are have a front sight around 1 meter from your eye, and the answer works out to +0.50 added, just like RobinC said. I also shoot smallbore with an 1827 Fortner or a 1913, and both of those work out to +0.50.
There are two ways to go about this - as I described, if you start with your distance prescription, I can do the math to adjust the lens you need for shooting (+0.5 for most rifles). The other option is to have your eye doc do it: measure the distance from the front sight to your eye, double that distance (so if it is 1 meter from your eye to the sight, use 2meters), have the eye doc put the vision chart at 2 meters, and measure you there. That lens power would be the one you need for shooting, and it will be +0.5 diopters higher in the sphere than your distance vision.
I do sell lenses, I can make any power you need, including astigmatism corrected lenses. Cost is $40 delivered in the US, though I imagine sending to Wales would not be much more.
In terms of the principles I am describing, they are all straight out of photography. Google 'hyperfocal' distance for a more in-depth explanation. But it is quite simple. THere are two things you need to do. Fist is to get your depth of field balanced so it falls evenly between the front sight and the target. This is accomplished by adjusting the lens strength, which moves your focal point. That is what the optical math I presented above does. This math is quite exact in terms of the relationship between this ideal focal point and your eye's optimal infinity focal point (aka your 'distance prescription'). The second thing you want to do is to get the largest depth of field possible. Depth of field is driven by aperture size. The smaller the aperture, the greater your depth of field. Unfortunately, a small aperture also limits light coming in, so the limit of aperture size is usually determined by when the image starts to go dim.
If you want to give your eye doc a 30 second education, say:
"I am trying to focus at the hyperfocal distance of my front sight, so my depth of field is evenly distributed between the front sight and the target. Does this make sense optically?"
The eye doc has studied this, and knows exactly what hyperfocal distances represent. The only issue is that very few human vision conditions require the eye to try and do this. So he studied this in school, and understands it, but has never thought about where it applies. If you get him thinking about hyperfocal, he will almost certainly immediately understand what you are trying to do, and set you right up.
In the interests of full disclosure, I am not a doctor, I am an engineer who knows optics. I own a small company, and make and sell lenses and other vision products for shooters. If you have a rifle, I also make a lens holder that inserts between the rear iris and the sight, that can hold the lens, and if you have astigmatism, it can rotate the lens to your best orientation.
In terms of taking my advice with a grain of salt - it is a fair position to question my reputation, as I am new to this forum, however I have been posting on usrifleteams (the old NationalMatch.co) for almost 10 years. Please google me or my company to see what people are saying.
Art Neergaard
ShootingSight LLC
www.shootingsight.com
shootingsight@nuvox.net
+1-513-702-4879
If it is rifle, substitute the front sight distance from your eye. I usually shoot high power, where most match rifles are have a front sight around 1 meter from your eye, and the answer works out to +0.50 added, just like RobinC said. I also shoot smallbore with an 1827 Fortner or a 1913, and both of those work out to +0.50.
There are two ways to go about this - as I described, if you start with your distance prescription, I can do the math to adjust the lens you need for shooting (+0.5 for most rifles). The other option is to have your eye doc do it: measure the distance from the front sight to your eye, double that distance (so if it is 1 meter from your eye to the sight, use 2meters), have the eye doc put the vision chart at 2 meters, and measure you there. That lens power would be the one you need for shooting, and it will be +0.5 diopters higher in the sphere than your distance vision.
I do sell lenses, I can make any power you need, including astigmatism corrected lenses. Cost is $40 delivered in the US, though I imagine sending to Wales would not be much more.
In terms of the principles I am describing, they are all straight out of photography. Google 'hyperfocal' distance for a more in-depth explanation. But it is quite simple. THere are two things you need to do. Fist is to get your depth of field balanced so it falls evenly between the front sight and the target. This is accomplished by adjusting the lens strength, which moves your focal point. That is what the optical math I presented above does. This math is quite exact in terms of the relationship between this ideal focal point and your eye's optimal infinity focal point (aka your 'distance prescription'). The second thing you want to do is to get the largest depth of field possible. Depth of field is driven by aperture size. The smaller the aperture, the greater your depth of field. Unfortunately, a small aperture also limits light coming in, so the limit of aperture size is usually determined by when the image starts to go dim.
If you want to give your eye doc a 30 second education, say:
"I am trying to focus at the hyperfocal distance of my front sight, so my depth of field is evenly distributed between the front sight and the target. Does this make sense optically?"
The eye doc has studied this, and knows exactly what hyperfocal distances represent. The only issue is that very few human vision conditions require the eye to try and do this. So he studied this in school, and understands it, but has never thought about where it applies. If you get him thinking about hyperfocal, he will almost certainly immediately understand what you are trying to do, and set you right up.
In the interests of full disclosure, I am not a doctor, I am an engineer who knows optics. I own a small company, and make and sell lenses and other vision products for shooters. If you have a rifle, I also make a lens holder that inserts between the rear iris and the sight, that can hold the lens, and if you have astigmatism, it can rotate the lens to your best orientation.
In terms of taking my advice with a grain of salt - it is a fair position to question my reputation, as I am new to this forum, however I have been posting on usrifleteams (the old NationalMatch.co) for almost 10 years. Please google me or my company to see what people are saying.
Art Neergaard
ShootingSight LLC
www.shootingsight.com
shootingsight@nuvox.net
+1-513-702-4879
Art is spot on in principle, and it works in many cases just to add 0.5 diopter to long vision which brings the focus to two metres which is accepted by opticians, even those with a lot of shooting experience as the best comprimise, BUT!
It also depends on the rear iris pulling the aiming mark into an acceptable degree of vision to refine the aim and this can be the problem as it is in my case. Different eyes and eye muscles react differently to light, I had to have the iris so tight to get target vision that in bright light I was OK but if the light fell a little I was doomed. The expert shooting optician does tests with test lens's at fore sight distance also uses an iris to get the best ballance of long vision with the same lens. For me he did a comprimise by taking out the focal length a slight amount, this works perfectly for me, and I'm aware of another shooter where a different comprimise worked better. So I would not disagree with anything that Art has said and he has explained it beautifully clearly, but I would always advise to see an expert shooting optician to get that finite variation around the +0.5 diopter that can make all the difference especially for us older shooters.
Good Shooting
Robin
It also depends on the rear iris pulling the aiming mark into an acceptable degree of vision to refine the aim and this can be the problem as it is in my case. Different eyes and eye muscles react differently to light, I had to have the iris so tight to get target vision that in bright light I was OK but if the light fell a little I was doomed. The expert shooting optician does tests with test lens's at fore sight distance also uses an iris to get the best ballance of long vision with the same lens. For me he did a comprimise by taking out the focal length a slight amount, this works perfectly for me, and I'm aware of another shooter where a different comprimise worked better. So I would not disagree with anything that Art has said and he has explained it beautifully clearly, but I would always advise to see an expert shooting optician to get that finite variation around the +0.5 diopter that can make all the difference especially for us older shooters.
Good Shooting
Robin
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ShootingSight
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The +0.5 represents the rounding of the lens that gets you to the hyperfocal point. That is the point at which your depth of field is spread evenly between the front sight and target, and when you calculate the size of the depth of field, based on the circle of confusion limits, the hyperfocal gives you the greatest depth of field possible, so in that regard, it is an optimum.
Now, simply centering your depth of field is not sufficient, you also need to increase your depth of field over what the pupil of the eye can do, otherwise your eye is focused out at 2 meters and both the front sight and the target look miserable.
For most people, an aperture of around 1mm will make both sight and target sufficiently clear, without dimming the image unacceptably. However, in low light situations, or if you have certain eye diseases that require you see more light, you could be forced to leave the aperture more open, resulting in greater blur on both the target and the front sight. In this case, rather than leaving your eye relaxed and accepting this blur, your brain will start flexing the ciliary muscle in your eye to bring the front sight into clearer focus.
Without getting into all the reasons why this is bad, suffice it to say that the shooter might elect to go 1 step higher in lens power, and add +0.75, rather than +0.50, making the front sight more clear, but giving up on target focus.
However since the cost is only $40 for a lens, and since most do not have this exception and find that +0.50 is sufficient, it makes much more sense to simply try the 0.5 and see if it works, rather than driving a distance to see a specialist doctor who will let you bring in a rifle to test with. When you consider that office lighting won't match range lighting anyhow, the benefit becomes even more questionable.
If you really are inclined to play with different powers, I sell diagnostic lens kits with either just positive powers from 0.25 to 1.25 in 1/4 steps, or else 1.5 to -1.5 in 1/4 steps. This way, you can go to the actual range, in the actual lighting conditions, and at the actual target distance, and try different lenses to see what you like best.
Art Neergaard
ShootingSight LLC
www.shootingsight.com
shootingsight@nuvox.net
+1-513-702-4879
Now, simply centering your depth of field is not sufficient, you also need to increase your depth of field over what the pupil of the eye can do, otherwise your eye is focused out at 2 meters and both the front sight and the target look miserable.
For most people, an aperture of around 1mm will make both sight and target sufficiently clear, without dimming the image unacceptably. However, in low light situations, or if you have certain eye diseases that require you see more light, you could be forced to leave the aperture more open, resulting in greater blur on both the target and the front sight. In this case, rather than leaving your eye relaxed and accepting this blur, your brain will start flexing the ciliary muscle in your eye to bring the front sight into clearer focus.
Without getting into all the reasons why this is bad, suffice it to say that the shooter might elect to go 1 step higher in lens power, and add +0.75, rather than +0.50, making the front sight more clear, but giving up on target focus.
However since the cost is only $40 for a lens, and since most do not have this exception and find that +0.50 is sufficient, it makes much more sense to simply try the 0.5 and see if it works, rather than driving a distance to see a specialist doctor who will let you bring in a rifle to test with. When you consider that office lighting won't match range lighting anyhow, the benefit becomes even more questionable.
If you really are inclined to play with different powers, I sell diagnostic lens kits with either just positive powers from 0.25 to 1.25 in 1/4 steps, or else 1.5 to -1.5 in 1/4 steps. This way, you can go to the actual range, in the actual lighting conditions, and at the actual target distance, and try different lenses to see what you like best.
Art Neergaard
ShootingSight LLC
www.shootingsight.com
shootingsight@nuvox.net
+1-513-702-4879
My apologies for the lack of thanks for your detailed replies, I've been having a spot of bother logging in.
For now as I don't shoot competitively a 12 - 14 hour round trip to Bedford seems a bit excessive, although I don't doubt for a second the results would be worth it.
Art, as you say $40 plus a few more for postage it's well worth a go if it's somewhere close, I'll be in touch when I get a prescription if that's OK.
I'm thinking (as I don't shoot competitively anymore) that the best option for me would be the Anschutz Mono Frame that screws onto the back of the rear sight, at £45 it's a whole heap cheaper than a set of frames and they would be permanently aligned, does anyone have an opinion of this bit of kit?
Many thanks again for your replies they have been very informative and helpful
Colin
For now as I don't shoot competitively a 12 - 14 hour round trip to Bedford seems a bit excessive, although I don't doubt for a second the results would be worth it.
Art, as you say $40 plus a few more for postage it's well worth a go if it's somewhere close, I'll be in touch when I get a prescription if that's OK.
I'm thinking (as I don't shoot competitively anymore) that the best option for me would be the Anschutz Mono Frame that screws onto the back of the rear sight, at £45 it's a whole heap cheaper than a set of frames and they would be permanently aligned, does anyone have an opinion of this bit of kit?
Many thanks again for your replies they have been very informative and helpful
Colin
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ShootingSight
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ShootingSight
- Posts: 318
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Nice one Art, that looks interesting, is there any advantage of having the lens upstream? I share my rifle with my wife at the moment, hoping to get her own soon. I take it that is easy to remove and replace without loosing the lens? The Anschutz one would just flip up out of the way.
I have seen some Centra and Gehmann iris' with a variable dioptre contraption (-4.5 to +4.5), any opinion on these? You won't be talking yourself out of a sale, I need to save up for my wife's gun before anything fancy like that
I have seen some Centra and Gehmann iris' with a variable dioptre contraption (-4.5 to +4.5), any opinion on these? You won't be talking yourself out of a sale, I need to save up for my wife's gun before anything fancy like that
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ShootingSight
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If you are sharing with your wife, my system has a slight disadvantage. Anytime you introduce a lens between the rear aperture and the target, it has the possibility of shifting your zero slightly, so everytime you remove/re-install mine, your zero might be off. This is not a problem if you get sighters, though the problem is eliminated for the Anschutz option (assuming you and your wife have the same zeros).
As to the adjustable diopters, I love them, and have several I bought used (new price is too dear for me). No messing with the lens strength calculation, you just look through them and dial till you like it. Also, your eyes can change subtly from day to day, so you can re-adjust every time. Now, once you adjust it correctly, you typically just leave it there, so the advantage of adjustability is really a one-time benefit. Given that these systems run $180 versus a $40 lens, so you are paying a steep premium for the ease of use. Cheaper would be to buy a few lenses of different powers, though it would not be as convenient.
As to the adjustable diopters, I love them, and have several I bought used (new price is too dear for me). No messing with the lens strength calculation, you just look through them and dial till you like it. Also, your eyes can change subtly from day to day, so you can re-adjust every time. Now, once you adjust it correctly, you typically just leave it there, so the advantage of adjustability is really a one-time benefit. Given that these systems run $180 versus a $40 lens, so you are paying a steep premium for the ease of use. Cheaper would be to buy a few lenses of different powers, though it would not be as convenient.
Thanks Art, my my wife and I do use the same zeros but to be honest it would do her no harm to fire off a couple of shots to reset after me. Seeing how cash is a little short at present one way or the other I will be in touch with you as soon as I have a prescription if that's OK. The chances are that once she gets her own gun I will stick with your option anyway as it looks very compact.
Many thanks again for your help. most informative.
Colin
Many thanks again for your help. most informative.
Colin
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peashooter
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If you have perfect vision avoid lens for rifle shooting, totaly uneccesary, but pistol is a totaly different propostion though.
Its also against ISSF rules which includes Air rifle and 50 mt smallbore rifle to have any magnifying lens attached to the rifle, if you need them they must be fitted into shooting spectacles.
Good shooting
Robin
Its also against ISSF rules which includes Air rifle and 50 mt smallbore rifle to have any magnifying lens attached to the rifle, if you need them they must be fitted into shooting spectacles.
Good shooting
Robin
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ShootingSight
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Yes, even if you have perfect vision, you can benefit from a lens. The benefit won't be as great, but it is more than zero.
When you are young, you can flex the eye muscle and deform the lens to add the +0.5 diopters you need. So adding a lens will not let you see better than you could normally see, however without the lens, you are holding the focus by keeping the eye muscle flexed, while with a lens you are getting the same focus while the eye muscle is relaxed.
So from an optical perspective, it is the same sight picture, but without any eye strain.
Now there are negatives to a lens, depending on how it is executed; they can fog, be dirty, get misaligned, .... so a young 'un might decide they are not worth the hassle, but in theory it is slightly better.
Art
When you are young, you can flex the eye muscle and deform the lens to add the +0.5 diopters you need. So adding a lens will not let you see better than you could normally see, however without the lens, you are holding the focus by keeping the eye muscle flexed, while with a lens you are getting the same focus while the eye muscle is relaxed.
So from an optical perspective, it is the same sight picture, but without any eye strain.
Now there are negatives to a lens, depending on how it is executed; they can fog, be dirty, get misaligned, .... so a young 'un might decide they are not worth the hassle, but in theory it is slightly better.
Art