I just recently (like yesterday) got a pair of Knobloch glasses and I had a couple of questions about them.
1. I have the centering device, but am kind of confused on how exactly it works. also, what is the best way to set up a pair of glasses?
2. The people at CC told me to buy three lenses and test them out to see which one works better and return the other two. I have really good vision, but an astigmatism in my aiming eye which makes it really hard to keep a good focus for a long time. The .75 diopter seems to work the best, but the target is fairly blurry. The weird thing is that the front sight is so clear that I can actually read the words written on the iris. I tried playing with the rearsight iris, but it doesn't seem to help that much. Is this normal? If not, how can I correct it?
Thanks!
Fuzzy Target
Moderators: pilkguns, Marcus, m1963, David Levene, Spencer
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David Levene
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Re: Fuzzy Target
Do the lenses you have include astigmatism correction.silentfury214 wrote:....but an astigmatism in my aiming eye....
If not then that could be a problem.
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silentfury214
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The "stock" pluse dipoter lenses (.50, .75, etc) have no other corrections to them. If your vision correction requires an astgimitism adjustment, you need to have it properly assessed and then a lens can be fitted to your lens holder when it is made. The lens will have the astigmitism and ditance corrections incorporated.
Dennis
Dennis
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silentfury214
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- Location: Tennessee
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silentfury214
- Posts: 186
- Joined: Thu Jun 24, 2010 9:07 am
- Location: Tennessee
Go look at the http://www.10pt9.com/Gear/Shooting-Glasses-c35/ website. See down at the bottom of the page
I got one about a month ago for $60
I got one about a month ago for $60
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David Levene
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The problem is that you need to know the amount and angle of correction for astigmatism (they seem to charge an extra $14 for the lens).jhmartin wrote:Go look at the http://www.10pt9.com/Gear/Shooting-Glasses-c35/ website. See down at the bottom of the page
I got one about a month ago for $60
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silentfury214
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I have never been prescribed glasses, but I haven't been to the optometrist for a few years. Last time I checked, I had 20/15 vision. He said I could wear glasses, but it wasn't necessary. At the last competition I shot at, I noticed that I had to really strain myself to focus while in prone, and I was reminded that I have an stigmatism. I did some research and found out that it causes poor focusing, so that is why I purchased the glasses. I hope to shoot in the Olympic Trials for 3p smallbore, and was hoping to have some help with my vision with a "quick fix" but obviously that isn't going to happen, so if you have any other tips, they are greatly appreciated.
Time is important in this case. See if there is a optical store in your area that has an on-site lab for grinding glasses. If there is, go to them with your prescription (most of these stores have opticians at their stores). Bring your frames and explain that you are going to the Olympic Trials and need their help. When you mention the Olympics, people are usually glad to help. Show them the lens holder and ask if they can grind a lens with your prescription that will fit that lens holder. Make sure that they understand that you will be looking through the center of the lens.
The only issue is size. If you have a 23 mm lens holder, it is difficult for some facilities to make lenses that small.
This is your best chance a getting a lens quickly.
The only issue is size. If you have a 23 mm lens holder, it is difficult for some facilities to make lenses that small.
This is your best chance a getting a lens quickly.
Yes, astigmatism will cause all sorts of problems with your sight picture as it's turning your circular target and sight elements oval...
It's entirely possible to get lenses that small, but you may have to explain to your optometrist exactly what you need and make sure they understand what your requirements are as they're not what (s)he will be used to dealing with.
The other option if time is of the essence is to enquire about contact lenses.
You can get contacts to correct astigmatism that are weighted at the bottom so they will sit and orient correctly. Depending on what local facilities are available that may be another option to tide you over.
Obviously contacts pose their own challenges, particularly for a 3x40 where you need to be aware of them drying out and perhaps pop some drops in between positions as required.
It's entirely possible to get lenses that small, but you may have to explain to your optometrist exactly what you need and make sure they understand what your requirements are as they're not what (s)he will be used to dealing with.
The other option if time is of the essence is to enquire about contact lenses.
You can get contacts to correct astigmatism that are weighted at the bottom so they will sit and orient correctly. Depending on what local facilities are available that may be another option to tide you over.
Obviously contacts pose their own challenges, particularly for a 3x40 where you need to be aware of them drying out and perhaps pop some drops in between positions as required.
In my area we have a very knowledgeable optometrist (Copper State Optical). He has actually called some of our matches.
I went to him with a prescription to correct my vision (astigmatism) and we tested with a gun in his office to get the correct diopter lens (+0.50) to get the focus on the front sight.
The next day I shot the highest AP score I had in a long time.
That's the way to go.
I went to him with a prescription to correct my vision (astigmatism) and we tested with a gun in his office to get the correct diopter lens (+0.50) to get the focus on the front sight.
The next day I shot the highest AP score I had in a long time.
That's the way to go.
I have astigmatism. I used to just use safety glasses. About 10 years ago one season my hp prone scores went into the 160's/200 where it was always in the mid to upper 190's. My first 5 shots were X's & 10's then dropped off once my eyes strained out from the astigmatism. Bought the champion glasses from CC with .25, .50 & .75 lenses. My scores improved for the season. I needed the 25mm lenses and extended nose piece. The next season scores started to drop again with the first 5 shots being in the X & 10 like before.
I contacted Neil Stepp at ISS http://www.iss-internationalshootersservice.com/
and he had 3 lenses made for me with my astigmatism correction along with .25 & .50 & .75 added. These worked great for several years and my scores had been in the mid to upper 190's.
Now it's hit or miss. I've tried a bloop tube and it's also hit or miss. I'm tired of buying new lenses every year and spend several trips to the range experimenting. I'm switching to smallbore prone where I can use a scope and the eye problem is no longer a problem. I still need shooting glasses to get the lens high and left so I have bifocal lens with my astigmatism correction and reading, still done by Neal Stepp. Give him a call and he'll get you what you need and he's a good guy as well.
Had a lens made last year with the bifocal and it was $65 shipped.
I contacted Neil Stepp at ISS http://www.iss-internationalshootersservice.com/
and he had 3 lenses made for me with my astigmatism correction along with .25 & .50 & .75 added. These worked great for several years and my scores had been in the mid to upper 190's.
Now it's hit or miss. I've tried a bloop tube and it's also hit or miss. I'm tired of buying new lenses every year and spend several trips to the range experimenting. I'm switching to smallbore prone where I can use a scope and the eye problem is no longer a problem. I still need shooting glasses to get the lens high and left so I have bifocal lens with my astigmatism correction and reading, still done by Neal Stepp. Give him a call and he'll get you what you need and he's a good guy as well.
Had a lens made last year with the bifocal and it was $65 shipped.
Seeing the optometrist is a great way to go and getting the glasses right. I'm sure most folks get their eyes checked every year or two and the prescription often changes (as you get older...). At the same time get your shooting glasses lenses checked and get a new lens if required. If you go from great shooting vision, to not so great it just shows your eyes have changed and the once great lens is no longer right for you.
Also once you talk it through and get it right once, you pretty much just need to keep the pattern the same. i.e. your shooting lenses just need a closer focus than you 'normal' lense by 0.25, 0.5 or whatever.
Rob.
Also once you talk it through and get it right once, you pretty much just need to keep the pattern the same. i.e. your shooting lenses just need a closer focus than you 'normal' lense by 0.25, 0.5 or whatever.
Rob.
i just took my frames with me to my optometrist and had them cut a lense to match my prescription last time i went....the look on their face was priceless when they tried to figure out what they were for.
i just had them center the focal point in the center of the lense, so that way i could adjust it myself.
i just had them center the focal point in the center of the lense, so that way i could adjust it myself.
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David Levene
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- Joined: Mon Mar 01, 2004 12:49 pm
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Re: Fuzzy Target
I've always subscribed to the notion that the point of focus of the lens should be slightly beyond the foresight.silentfury214 wrote:The .75 diopter seems to work the best, but the target is fairly blurry. The weird thing is that the front sight is so clear that I can actually read the words written on the iris. I tried playing with the rearsight iris, but it doesn't seem to help that much.
i.e. the foresight should be slightly out of focus as well as the target.
That seems to give me the best compromise between the two anyway...
If you're focused on the foresight the target will be blurry - you can try and increase the depth of field by closing down the iris but that brings a different set of problems.
What you don't want is to be focused on the target with a blurry foresight.
Just my 2¢.
Ken.
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ShootingSight
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- Contact:
New member here, and I can solve your problems.
I am an engineer, studied optics some, I am a highpower shooter, and a photography enthusiast, so I know lens equations, I know shooters needs, and I make custom lenses. I can make astigmatic lenses. Turnaround time is usually under a week. My lenses are $40 delivered, and 23mm Knobloch is no problem - I cut them on a lathe, so I can actually do any diameter you want, down to about 3/16". All my lenses are impact resistant polycarbonate, and are Anti-Reflective coated.
I spec lenses based on math and photography formulas, calculated using your actual sight radius. None of this try 3 lenses and send 2 back nonsense.
So, with that introduction, here is how optical physics works:
KennyB hit the nail on the head. You do want to focus beyond the front sight. Most shooters and eye docs don't get this, and prescribe wrong because of it.
Any lens/aperture system (ie your eye and pupil) have a natural depth of field. If that depth of field is small, you are kind of screwed, because you can focus on either the target or the sight, but not both. However, if you make that depth of field big, and you adjust your focus so the depth of field is centered between your sights and the target, you can actually create a situation where the target and the sights are is sharp focus at the same time, because the sights are at the near edge of the depth of field at the same time as the target is at the far edge of the depth of field. You see photographers doing this all the time - a pretty girl is in sharp focus, and the mountains behind her are in sharp focus as well. The way this is done requires two things: using a small aperture to create a big depth of field, and adjusting the lens in your camera to balance your depth of field between the girl and the mountain.
So, let's address focus first. Where do you want to focus? To split your depth of field between two objects requires some math which I will not go into here, but when one of the objects is effectively at optical infinity, as your target is, the math simplifies. TO split your focus between a near object and infinity you want to focus at 2x the distance to the near object. This is called your hyperfocal distance. So, aim your pistol, have a laboratory assistant take out a ruler, and without poking you in the eye, measure the distance from your eye to the rear sight.
Example: let's pretend that distance is 24". Your hyperfocal distance that you want to focus at would be 48".
Next question is how you do that. The relaxed eye focuses at infinity, and to focus up close you have to exert the eye muscle, the cilary. Natural point of aim principles say that you would rather not exert a muscle, and further, as you get old and presbiopic you might not be able to pull your focus back to 48", and especially not to hold it there for a minute as you aim and shoot. So, the other way to move your focal point is to add a lens, which shifts your focus while leaving your eye muscle relaxed. How much lens? Lens power in diopter is simply the inverse of a lens focal length, in metric. A 2 diopter lens will focus you at 1/2 meter. A 3 diopter focuses you at 1/3 meter, etc.
So, if your hyperfocal distance is 48", convert this to metric, that is 1.22 meters. THe lens you would want is the inverse of 1.22, or 1/1.22 = 0.82. You would want a 0.82 diopter lens. Lenses actually come in 0.25 steps, and you always want to round down (I won't go into why here), so 0.82 becomes 0.75 diopters is your shooting lens if you do not wear glasses for distance vision correction.
Now, if you cannot see distance clearly, but need distance glasses (reading glasses do not count), and/or if you have an astigmatism, what you need to do is see an eye doc, and get a distance vision correction. You would then take that prescription, and add the +0.75 to the first (spherical) number, and that revised prescription is your ideal shooting lens.
That gets your focus centralized. Next step is making your depth of field as big as possible. To do this, you want a small aperture. In cameras, apertures are adjustable, so the photographer simply sets it. In your eye, the pupil is the aperture, and it varies with light, and it also has a minimum size of around 1/8". You can decrease your aperture size further by using a peep sight. THe smaller you go, the better your depth of field and the better your focus. Minimum size is dictated by brightness - small apertures limit light coming through, so at some point the image dims.
Solution is to get a small aperture on your glasses. Again, I have just started experimenting with making self-adhesive apertures for lenses. With one of these, the front sight and the target will be in perfect simultaneous focus. I'll set you up with a set.
Please feel free to respond to
shootingsight@nuvox.net
or call me at 513-702-4879
if you want to discuss further, but I can make this work, and if you are trying out for the olympics, I will jump through hoops to get you what you need in the fastest possible timing.
Regards,
Art Neergaard
PS, first step you can take ASAP is to go to an optometrist and get measured. WalMart optometrist is fine, it'll probably cost $40 and take 15 minutes. With that prescription, I can do all the math necessary to get you the lens you need. I can mark the orientation for astigmatism, though usually I prefer to give you a special target to look at, and instructions on how to twist the lens till you see the focus get the best possible.
I am an engineer, studied optics some, I am a highpower shooter, and a photography enthusiast, so I know lens equations, I know shooters needs, and I make custom lenses. I can make astigmatic lenses. Turnaround time is usually under a week. My lenses are $40 delivered, and 23mm Knobloch is no problem - I cut them on a lathe, so I can actually do any diameter you want, down to about 3/16". All my lenses are impact resistant polycarbonate, and are Anti-Reflective coated.
I spec lenses based on math and photography formulas, calculated using your actual sight radius. None of this try 3 lenses and send 2 back nonsense.
So, with that introduction, here is how optical physics works:
KennyB hit the nail on the head. You do want to focus beyond the front sight. Most shooters and eye docs don't get this, and prescribe wrong because of it.
Any lens/aperture system (ie your eye and pupil) have a natural depth of field. If that depth of field is small, you are kind of screwed, because you can focus on either the target or the sight, but not both. However, if you make that depth of field big, and you adjust your focus so the depth of field is centered between your sights and the target, you can actually create a situation where the target and the sights are is sharp focus at the same time, because the sights are at the near edge of the depth of field at the same time as the target is at the far edge of the depth of field. You see photographers doing this all the time - a pretty girl is in sharp focus, and the mountains behind her are in sharp focus as well. The way this is done requires two things: using a small aperture to create a big depth of field, and adjusting the lens in your camera to balance your depth of field between the girl and the mountain.
So, let's address focus first. Where do you want to focus? To split your depth of field between two objects requires some math which I will not go into here, but when one of the objects is effectively at optical infinity, as your target is, the math simplifies. TO split your focus between a near object and infinity you want to focus at 2x the distance to the near object. This is called your hyperfocal distance. So, aim your pistol, have a laboratory assistant take out a ruler, and without poking you in the eye, measure the distance from your eye to the rear sight.
Example: let's pretend that distance is 24". Your hyperfocal distance that you want to focus at would be 48".
Next question is how you do that. The relaxed eye focuses at infinity, and to focus up close you have to exert the eye muscle, the cilary. Natural point of aim principles say that you would rather not exert a muscle, and further, as you get old and presbiopic you might not be able to pull your focus back to 48", and especially not to hold it there for a minute as you aim and shoot. So, the other way to move your focal point is to add a lens, which shifts your focus while leaving your eye muscle relaxed. How much lens? Lens power in diopter is simply the inverse of a lens focal length, in metric. A 2 diopter lens will focus you at 1/2 meter. A 3 diopter focuses you at 1/3 meter, etc.
So, if your hyperfocal distance is 48", convert this to metric, that is 1.22 meters. THe lens you would want is the inverse of 1.22, or 1/1.22 = 0.82. You would want a 0.82 diopter lens. Lenses actually come in 0.25 steps, and you always want to round down (I won't go into why here), so 0.82 becomes 0.75 diopters is your shooting lens if you do not wear glasses for distance vision correction.
Now, if you cannot see distance clearly, but need distance glasses (reading glasses do not count), and/or if you have an astigmatism, what you need to do is see an eye doc, and get a distance vision correction. You would then take that prescription, and add the +0.75 to the first (spherical) number, and that revised prescription is your ideal shooting lens.
That gets your focus centralized. Next step is making your depth of field as big as possible. To do this, you want a small aperture. In cameras, apertures are adjustable, so the photographer simply sets it. In your eye, the pupil is the aperture, and it varies with light, and it also has a minimum size of around 1/8". You can decrease your aperture size further by using a peep sight. THe smaller you go, the better your depth of field and the better your focus. Minimum size is dictated by brightness - small apertures limit light coming through, so at some point the image dims.
Solution is to get a small aperture on your glasses. Again, I have just started experimenting with making self-adhesive apertures for lenses. With one of these, the front sight and the target will be in perfect simultaneous focus. I'll set you up with a set.
Please feel free to respond to
shootingsight@nuvox.net
or call me at 513-702-4879
if you want to discuss further, but I can make this work, and if you are trying out for the olympics, I will jump through hoops to get you what you need in the fastest possible timing.
Regards,
Art Neergaard
PS, first step you can take ASAP is to go to an optometrist and get measured. WalMart optometrist is fine, it'll probably cost $40 and take 15 minutes. With that prescription, I can do all the math necessary to get you the lens you need. I can mark the orientation for astigmatism, though usually I prefer to give you a special target to look at, and instructions on how to twist the lens till you see the focus get the best possible.