Rear sight with corrective diopter?

[Mtl_Biker]

My vision is not very good and I wear progressive eyeglasses. Also I'm left eye dominant but strongly right-handed. With pistol I aim with my left eye and shoot right-handed, but have shooting glasses with a corrective lens set for my front sight distance plus an adjustable iris. I'm quite pleased with my pistol shooting results.

With 10-meter rifle however, I'm really not shooting well (about 50+ points worse than pistol, in a 60-shot match) and I'm trying to figure out what I might do to improve. I shoot rifle right-handed also, but aim with my right (non-dominant) eye and I have a blinder attached to my rear sight so that I can keep my left eye open without strain (or effect on my aiming). If I shoot any of my scoped rifles I shoot really very well so I'm pretty steady, but it's just with the standard sights on my FWB 800 Evolution Top that I have poor results. I think it is because I don't see the front sight clearly enough.

Do you think that one of the rear sights with corrective diopter and adjustable iris might help me? I believe such sights are now permitted in competition... is that right?

I'm thinking of something like this:

http://www.ebay.ca/itm/530-Gehmann-Rear ... 4d3f3c059e

or maybe the Gehmann 570-R with six color filters.

Any advice?

[Tim S]

Firstly, no I don't believe that adjustable focus lenses are permitted in competition yet. You may attach a prescription lens to the rear sight though, rather than wear it in glasses.

In terms of vision, most rifle shooters want their focus to be a little ahead of the foresight, not dead on it, making the target a little more clear. Typically prescriptions are distance +0.5. So if you're using a lens prescribed for pistol shooting, this may not be ideal for rifle.

It's also possible that your sub-optimal sight picture is caused by something else. Eye relief, foresight aperture, cheek piece set-up, can all affect your aim. I'd also ask what material your blinder is; normally translucent material is recommended, so yours eyes react equally and aren't strained, but anecdotally these cross-dominant shooter's seem to find a black/dark blinder more effective at occluding the dominant eye.

[Mtl_Biker]

Firstly, no I don't believe that adjustable focus lenses are permitted in competition yet. You may attach a prescription lens to the rear sight though, rather than wear it in glasses.

In terms of vision, most rifle shooters want their focus to be a little ahead of the foresight, not dead on it, making the target a little more clear. Typically prescriptions are distance +0.5. So if you're using a lens prescribed for pistol shooting, this may not be ideal for rifle.

It's also possible that your sub-optimal sight picture is caused by something else. Eye relief, foresight aperture, cheek piece set-up, can all affect your aim. I'd also ask what material your blinder is; normally translucent material is recommended, so yours eyes react equally and aren't strained, but anecdotally these cross-dominant shooter's seem to find a black/dark blinder more effective at occluding the dominant eye.

Thank you for your comments, Tim.

My binder is a white translucent one. Maybe I'll stick some black tape on mine to see if it's better/worse.

So the adjustable focus lenses aren't permitted... but a corrective lens is? I just found a corrective lens holder and the information on the web site may not be up-to-date, but it says that it is not permitted for competition nor is it ISSF approved. http://www.ebay.ca/itm/New-Gehmann-501- ... 569501cebc

There is no such disclaimer for the Gehmann 570 rearsight with iris and it says "correction from -4.5 to +4.5 diopter". Is that adjustable focus? Is that the same thing as eyesight correction? (Dumb question?) http://www.ebay.ca/itm/570-Gehmann-Rear ... 4d3ad792c7

Okay, if I'm not going to be in any ISSF events, what do you (all) think about the choice of getting a lens holder and then a custom lens (which would have to be changed as my eyesight changes) or the Gehmann #579 CLS Vari-Focus Astigmatic Iris System? http://www.ebay.ca/itm/Gehmann-579-CLS- ... 9530a2ca48

Thanks again for any help and advice.

[Tim S]

Yes a single corrective lens is permitted, but not adjustable dioptre lenses. The -4.5 / + 4.5 you mention is the correction range of the internal lens, from -4.5 dioptres (very shortsighted) to +4.5 dioptres (very long sighted). If I were to use one, I'd set it at about +1.5 as I'm long sighted, but don't need a large correction. The lens also magnifies everything by 1.5X, which some shooters find useful - when allowed under domestic rules. There will be a further set of numbers at the very back of the unit; these are for the aperture, 1.1-1.2mm would be a good starting point under decent light. As a rule, avoid setting the aperture super tight, although you may find the sight picture is sharper, it may be a bit gloomy and tiring.

The rule change allowing a corrective lens to be mounted on the rifle is very recent, so the eBay seller may not have been aware, although some certainly are; I think I saw Peter Sidi using a lens holder in the 3x40 Final at the Delhi World Cup. ISSF/UIT rules have prohibited adjustable dioptre lenses for many years, so that seller may not have thought it necessary to add the caveat.

It sounds as if you need in person advice. If there are no certified coaches near you, what about experienced shooters who would give you feedback about your position? The FWB 800 is a complex rifle, and new shooters will rarely have to adjust the stock for fit totally on their own.

[Mtl_Biker]

Yes a single corrective lens is permitted, but not adjustable dioptre lenses. The -4.5 / + 4.5 you mention is the correction range of the internal lens. If I were to use one I'd set it at about +1.5 as I'm slightly long sighted. The lens also magnifies everything by 1.5X. There will be a further set of numbers at the very back; these are for the aperture, 1.1-1.2mm would be a good startng point under decent light.

The rule change allowing a corrective lens to be mounted on the rifle is very recent, so the eBay seller may not have been aware. I think I saw Peter Sidi using a lens holder in the 3x40 Final at the Delhi World Cup.

It sounds as if you need in person advice. If there are no certified coaches near you, what about experienced shooters who would give you feedback about your position? The FWB 800 is a complex rifle, and new shooters will rarely have to adjust the stock for fit totally on their own.

Thank you (again!), Tim.

I currently have an adjustable iris on my rear sight, but it offers no magnification. I think I'll give that adjustable dioptre lens a try, understanding that it wouldn't be allowed in any serious competition. And yes, I did see that Peter Sidi was using a lens holder, which is why I started looking into this possibility. With such a device, do you think I should remove my progressive eyeglasses, or leave them on? I know (believe) that my eyeglasses are not well-suited for rifle shooting the way they are but maybe with the addition of the adjustable diopter it would be better.

I did have an experienced coach (not sure if he's certified or not, but he's been coaching juniors and cadets for several years) give me some help adjusting my 800. When I got it, I first set it to what I was used to (from my FWB 602) and was comfortable, but then with the help of that coach, I found it was totally wrong. So the rifle now is adjusted much more appropriately for me. Made an amazing difference.

Cheers!

[Tim S]

The adjustable dioptre will normally replace your glasses*. In theory you could use the dioptre just for the extra correction for a balanced sight picture, although as your regular glasses are varifocal and won't place the lens correctly, I'd just use the dioptre, unless you need an astigmatism correction, or you need more than 4.5 dioptres correction. In either of the later cases, a lens prescribed specifically for shooting in a holder or frames would be better than varifocals + dioptre.

Access to a coach, even an enthusiastic amateur, does make a big difference.

*It's not an issue for AR, but I know of prone shooters who need glasses to see wind flag with their non-aiming eye. Several chose shooting specs with two lenses, general and shooting-specific, but one had a distance lens clipped to the top of his spotting scope.

[Mtl_Biker]

The adjustable dioptre will normally replace your glasses*. In theory you could use the dioptre just for the extra correction for a balanced sight picture, although as your regular glasses are varifocal and won't place the lens correctly, I'd just use the dioptre, unless you need an astigmatism correction, or you need more than 4.5 dioptres correction. In either of the later cases, a lens prescribed specifically for shooting in a holder or frames would be better than varifocals + dioptre.

Access to a coach, even an enthusiastic amateur, does make a big difference.

*It's not an issue for AR, but I know of prone shooters who need glasses to see wind flag with their non-aiming eye. Several chose shooting specs with two lenses, general and shooting-specific, but one had a distance lens clipped to the top of his spotting scope.

Thank you. I'll give it a try without my normal (progressive) eyeglasses.

Interesting info I was just told by my dealer (Cibles Canada Targets) who has always been superb and very well-informed... They told me that magnification in the rear sight is not allowed under ISSF rules but that corrective lenses are allowed. Including those which are variable diopter correction. And even more surprising is that the model #530 (which I ordered) with correction and 1.5 diopter magnification was CAD$205, while the newer model #530-0 with the same correction but without the magnification was CAD$495!!!!!!! They explained that the 530-0 was also newer stock and that all Gehmann prices had been going up a lot, plus it had some red trim which of course :) costs more.

With any luck it'll arrive tomorrow or Wednesday and I'll be able to try it out.

Cheers!

[Tim S]

The non-magnifying Gehmann dioptre is quite new, and I think the first of its kind. The lens arrangement in older models also magnify, and always have. I imagine this explains the hefty price difference.

[mobarron]

If you do decide to try a variable rear diopter, borrow one first. Some shooter's use these very successfully but other have trouble. Mike Barron

[Mtl_Biker]

If you do decide to try a variable rear diopter, borrow one first. Some shooter's use these very successfully but other have trouble. Mike Barron

No one I know has one, so I couldn't borrow one first. So I ordered it, and it should arrive today. Plus I have a 7-day return with it in case it's not suitable.

I can't wait to try it.

[Mtl_Biker]

Sometimes in my enthusiasm I do things too quickly...

I had a consult with my optician this morning and because I also have astigmatism, he said that absolutely positively I will not like the #530 adjustable diopter iris I ordered. The 530 has just arrived, and I'm not even going to try it (my rifle is at home anyway) and will return it to my dealer. I've ordered as a replacement, the #579 Cylindrical lens system (which DOES correct for astigmatism) with #570 6-color iris with 1.5x diopter magnification.

But I'm going to have to wait about two weeks to get this because he's out of stock of the 570.

Waiting impatiently. :)

[Paul]

I thought that the 530 could also correct astigmatism ?

Take a look at the Gehmann website: http://gehmann.com/english/products.php ... 20&id=1639

The advantage compared to usual shooters‘ frames is the possibility to correct the spherical and astigmatic defect through slight fine adjustments any time, while neglecting the need of time-consuming shooting frame setups.

[Mtl_Biker]

I thought that the 530 could also correct astigmatism ?

Take a look at the Gehmann website: http://gehmann.com/english/products.php ... 20&id=1639

The advantage compared to usual shooters‘ frames is the possibility to correct the spherical and astigmatic defect through slight fine adjustments any time, while neglecting the need of time-consuming shooting frame setups.

Not quite so. The link you gave is for the new 50300-0 diopter with ZERO magnification. That's what's special about that model. And the description does say, "In combination with our cylindrical lens system 579 for shooters of all classifications, we are finally able to provide a 100 % substitute for shooting glasses without any magnification which can be used by all shooters."

So you need the 579 for astigmatism correction, PLUS the diopter of your choice, whether with or without magnification or further diopter correction. So I opted for the 579 to help correct my astigmatism, plus the 570 to further correct my poor vision and also to have the 1.5x magnification (since I'm FAR FAR AWAY from shooting in any competitive ISSF event).

[ShootingSight]

So there is an easier and MUCH cheaper way to fix this - by doing the optical math and just get the right lens in the first place.

Older adjustable diopters are the easy way to get there, because you just turn it till it looks right, however once you get it to the right place you usually don't need to adjust it again unless your vision changes. Adjustable diopters with cylinder correction are crazy expensive and difficult to adjust, but again, if you do the optical math, totally unnecessary.

The solution has been mentioned above, sort of.

The answer in most match rifles is to add +0.50 diopters to your distance vision. This will shift your eye's relaxed focal point to 2 meters (diopters are the inverse of focal length, in meters, so a 1/2 diopter lens will focus at 2 meters). This distance is calculated to have you focus at what in optical physics is called your hyperfocal distance, which is the half way point between focusing on the front sight,and focusing on the target. This way, your eye's depth of field remains centered between the two, and as you decrease your aperture size, your depth of field eventually becomes large enough that the front sight falls inside the near edge of your depth of field at the same time as the target falls in the far edge of your depth of field, and you can see them both together clearly.

So, go to your eye doc, and get a new prescription. If you have an astigmatism, it will have 3 numbers: a sphere value that is there to adjust your relaxed focal point in/out, and is set by the eye doc so your relaxed focal point falls at infinity. Then there are cylinder and axis values that compensate for your astigmatic error (these are zero, and are omitted if you do not have an astigmatism). Don't change these. The sphere value could be positive or negative, so pay attention. You want to add +0.50 to the sphere value, so if you are a -1.25 for distance, you want to make it a -0.75 for shooting. If you are +1.25 for distance, make it +2.00. Lenses can be Right/Left, or OD/OS. OD is right, OS is left.

You can put this corrected lens in eyeglasses you get from the doc, or I can supply round lenses to fit in Knobloch style glasses, or I make a small holder that lets you screw a pill-size lens into the rear sight. My lenses are $40 delivered, and another $30 for the rear sight lens holder - a far cry cheaper than the adjustable iris.

DO NOT get progressive or no-line bifocal lenses. If you want a bifocal to see your notebook, get the old fashioned type with a line, so you know what part of the lens you are looking for. If you do get a bifocal, I recommend an extra strong one, like +2.5 or +3.00 over your distance vision (ie a 1/3 meter, or 12" focus), so you can see WAY up close. This way, if you are slung in for prone, you can still focus on the marks on the sight without breaking position.

[Mtl_Biker]

So there is an easier and MUCH cheaper way to fix this - by doing the optical math and just get the right lens in the first place.

Older adjustable diopters are the easy way to get there, because you just turn it till it looks right, however once you get it to the right place you usually don't need to adjust it again unless your vision changes. Adjustable diopters with cylinder correction are crazy expensive and difficult to adjust, but again, if you do the optical math, totally unnecessary.

The solution has been mentioned above, sort of.

The answer in most match rifles is to add +0.50 diopters to your distance vision. This will shift your eye's relaxed focal point to 2 meters (diopters are the inverse of focal length, in meters, so a 1/2 diopter lens will focus at 2 meters). This distance is calculated to have you focus at what in optical physics is called your hyperfocal distance, which is the half way point between focusing on the front sight,and focusing on the target. This way, your eye's depth of field remains centered between the two, and as you decrease your aperture size, your depth of field eventually becomes large enough that the front sight falls inside the near edge of your depth of field at the same time as the target falls in the far edge of your depth of field, and you can see them both together clearly.

So, go to your eye doc, and get a new prescription. If you have an astigmatism, it will have 3 numbers: a sphere value that is there to adjust your relaxed focal point in/out, and is set by the eye doc so your relaxed focal point falls at infinity. Then there are cylinder and axis values that compensate for your astigmatic error (these are zero, and are omitted if you do not have an astigmatism). Don't change these. The sphere value could be positive or negative, so pay attention. You want to add +0.50 to the sphere value, so if you are a -1.25 for distance, you want to make it a -0.75 for shooting. If you are +1.25 for distance, make it +2.00. Lenses can be Right/Left, or OD/OS. OD is right, OS is left.

You can put this corrected lens in eyeglasses you get from the doc, or I can supply round lenses to fit in Knobloch style glasses, or I make a small holder that lets you screw a pill-size lens into the rear sight. My lenses are $40 delivered, and another $30 for the rear sight lens holder - a far cry cheaper than the adjustable iris.

DO NOT get progressive or no-line bifocal lenses. If you want a bifocal to see your notebook, get the old fashioned type with a line, so you know what part of the lens you are looking for. If you do get a bifocal, I recommend an extra strong one, like +2.5 or +3.00 over your distance vision (ie a 1/3 meter, or 12" focus), so you can see WAY up close. This way, if you are slung in for prone, you can still focus on the marks on the sight without breaking position.

Most helpful message. Thank you.

Too late for me now, as I've ordered (and already paid for) the Gehmann combo I mentioned... the #570-579.

Do the lenses you offer do anything for astigmatism? My right eye values are: Sphere +2.25, Cylinder -1.00, Axis 115, and Add +2.50 (which I guess is for reading).

I wonder how practical (if at all) it would be to set up a pair of Knobloch style glasses with the left eye set for pistol shooting (which I already have) but the right eye set for rifle. Probably not very practical because I'd have to figure out a way to block the non-aiming eye and very often I shoot BOTH pistol and rifle matches in the same evening.

[ShootingSight]

Absolutely my lenses will fix astigmatism. The +0.50 number I calculated is the number you add to your distance correction values, which include your astigmatism correction.

Lens diopters are additive. Stack a 2 diopter lens on top of a 1 diopter lens, and it is the same as having a 3 diopter lens. If you have an astigmatism, it means the lens in your eye does not have a spherical surface, but it has a bulge in one direction, so it is shaped more like looking sideways through a football - ie you have a sharper radius of curvature in one direction versus the perpendicular direction.

THe solution is that they give you a football shaped lens, with the same degree of difference between the curves as your eye, and you orient it so the direction of greatest curvature is at 90 degrees to the direction of curvature in your eye. So when you go around your eye and add the eye plus the lens, everywhere the eye is fat, the lens is thin, and everywhere the eye is thin, the lens is fat, so it adds to a constant valu all the way around. The orientation the lens has to be is the axis in your prescription. Curiously, if you rotate an astigmatism corrected lens by 90 degrees, it will make your astigmatism 2x as bad, as both thin sections align, and both thick sections align. Indeed, this is why I like round lenses for shooting, because you can actually stand in front of an image, and rotate the lens slightly, and see the focus come in and go out as you pass your correct orientation.

So with your adjustable, there are two cylinder lenses. YOu will need to rotate them relative to each other to determine the total cylinder strength, then you will need to rotate them together relative to your eye to align them to your axis. I'm sure they come with very complete instructions.

As to your 2-lens idea, I don't see why not. Shooting supply places make clip-on translucent blinders that attach to your glasses, so you just move it from clipping on one side to the other.

[Bryan996]

Sometimes in my enthusiasm I do things too quickly...

I had a consult with my optician this morning and because I also have astigmatism, he said that absolutely positively I will not like the #530 adjustable diopter iris I ordered. The 530 has just arrived, and I'm not even going to try it (my rifle is at home anyway) and will return it to my dealer. I've ordered as a replacement, the #579 Cylindrical lens system (which DOES correct for astigmatism) with #570 6-color iris with 1.5x diopter magnification.

But I'm going to have to wait about two weeks to get this because he's out of stock of the 570.

Waiting impatiently. :)

I have an astigmatism and use the new gehmann 50300 in combination with shooting glasses and its the best solution for me. The lens in my glasses corrects the astigmatism and then I can dial in the 50300 to give me perfect focus on the foresight. I'm over the moon with the 50300 even despite its cost. Most of my shooting is in the evening after work and the 50300 allows me to dial my eyes in as they change with fatigue, hydration and even sugar levels. Using a lens in glasses is a lot slimer option than the gehmann 579 option.

[Mtl_Biker]

I have an astigmatism and use the new gehmann 50300 in combination with shooting glasses and its the best solution for me. The lens in my glasses corrects the astigmatism and then I can dial in the 50300 to give me perfect focus on the foresight. I'm over the moon with the 50300 even despite its cost. Most of my shooting is in the evening after work and the 50300 allows me to dial my eyes in as they change with fatigue, hydration and even sugar levels. Using a lens in glasses is a lot slimer option than the gehmann 579 option.

What iris are you using with the 50300? Once you add an iris isn't the size up there comparably to the 570-579?

Did you have your eyeglasses specifically made for shooting? I'm guessing they're not a "progressive" prescription as mine are. Which is why I went for the 570-579 combo. With it I SHOULD be able to also get perfect focus on the foresight, even if I'm tired or sugar levels, etc. have changed. I wonder, does astigmatism also change with these factors, or not?

Another reason I went with the 570 is for the 6 colors... should be able to get optimum contrast in almost any lighting.

Cheers!

[Bryan996]

I've just fitted it to my 569 unit for indoors.

My frame lens is my normal prescription as the +0.5 doesn't work for me (I did have a lens made up to try it). The good thing with the 530 is that you can dial in the +0.5 if you need it. I can get the best image I've ever had. I would add that most of my focusing problems seem to be due to the light levels at our 25yd indoor range and the fact I'm shooting at the end of the day. I don't seem to need the 530 unit for my 50m sights as the light levels are better outside.

I don't believe astigmatism changes with hydration etc. The one thing I would say is that with the 570-579 you'll need to check the unit is set up to match any cant angle you have in the rifle and your head. If the unit doesn't align with your eye correctly it could make matters worse (if you've dialled it into your persciption rather than working it out in position). Glasses always keep the lens aligned to you eye. Indoors I also use the green filter for the best contrast.

Sorry to complicate your situation.

[Anschutz]

So there is an easier and MUCH cheaper way to fix this - by doing the optical math and just get the right lens in the first place.

Older adjustable diopters are the easy way to get there, because you just turn it till it looks right, however once you get it to the right place you usually don't need to adjust it again unless your vision changes. Adjustable diopters with cylinder correction are crazy expensive and difficult to adjust, but again, if you do the optical math, totally unnecessary.

The solution has been mentioned above, sort of.

The answer in most match rifles is to add +0.50 diopters to your distance vision. This will shift your eye's relaxed focal point to 2 meters (diopters are the inverse of focal length, in meters, so a 1/2 diopter lens will focus at 2 meters). This distance is calculated to have you focus at what in optical physics is called your hyperfocal distance, which is the half way point between focusing on the front sight,and focusing on the target. This way, your eye's depth of field remains centered between the two, and as you decrease your aperture size, your depth of field eventually becomes large enough that the front sight falls inside the near edge of your depth of field at the same time as the target falls in the far edge of your depth of field, and you can see them both together clearly.

So, go to your eye doc, and get a new prescription. If you have an astigmatism, it will have 3 numbers: a sphere value that is there to adjust your relaxed focal point in/out, and is set by the eye doc so your relaxed focal point falls at infinity. Then there are cylinder and axis values that compensate for your astigmatic error (these are zero, and are omitted if you do not have an astigmatism). Don't change these. The sphere value could be positive or negative, so pay attention. You want to add +0.50 to the sphere value, so if you are a -1.25 for distance, you want to make it a -0.75 for shooting. If you are +1.25 for distance, make it +2.00. Lenses can be Right/Left, or OD/OS. OD is right, OS is left.

You can put this corrected lens in eyeglasses you get from the doc, or I can supply round lenses to fit in Knobloch style glasses, or I make a small holder that lets you screw a pill-size lens into the rear sight. My lenses are $40 delivered, and another $30 for the rear sight lens holder - a far cry cheaper than the adjustable iris.

DO NOT get progressive or no-line bifocal lenses. If you want a bifocal to see your notebook, get the old fashioned type with a line, so you know what part of the lens you are looking for. If you do get a bifocal, I recommend an extra strong one, like +2.5 or +3.00 over your distance vision (ie a 1/3 meter, or 12" focus), so you can see WAY up close. This way, if you are slung in for prone, you can still focus on the marks on the sight without breaking position.

Art,
I've used your test lens kit successfully, for irons, with my old eyes. Have a question and sending a PM.
Thanks.