edster99 wrote:I've been trying to think it through and work out what is going on with a shooting glass lens - not something I've ever thought about before ! It seems to me that the astigmatism correction has to be worth having. Then its just a case of getting the focus point in the right place.
Am I right in thinking that the focus points should be in the following order with the noted glasses prescriptions ? Obviously I'm not sure of the exact place....
My Eye Rear Sight 0.0 -0.25 ForeSight -0.5 Further away -0.75 Target
cheers
Ed
For my eyes, as the diopter number of the correcting lens increases (becomes more positive), my eye can focus on closer objects. Thus my distance vision lens is +0.5, my reading distance vision lens is +2.50, and my pistol shooting distance lens is +1.5 for my short barrel IZH and +1.25 for my free pistol.
I have also found that my ability to achieve a sharp focus on my front sight can change by 0.25 diopter, depending on what I've eaten, how tired I am, etc. I either change lens or close down my iris a bit (I usually keep it full open) to accommodate.
AAlex wrote:Problems with astigmatism can be managed with adjustable iris.
If you don't have one, try making small holes of various sizes on a piece of electrical tape and attaching it to your glasses and see if it makes things better.
"Managed" .... I would suggest that depends on there definition of the term.
Yes an iris will "improve" many things and probably reduce the effect of astigmatism but that is not the point of and iris and can lead to many bad side affects. A proper lens and proper lighting is the real answer.
Just tried out my £11 specs and made a very noticeable difference - I can keep the foresight in focus and the target blurry, even at the range where the targets are bright and the shooting point is black !! Added another 8 points to my PB (345 out of 400) but then I have only been shooting about 3 weeks, and only had my own pistol - LP2 - for 4 days. But its a hell of a lot easier !!
I needed an AP glasses because with my normal glasses I could not focus on the front sight at all.
I took my AP to my eye docs office to get her to fit me with a pair of glasses. Turned out that Warrens recommendation (http://www.pilkguns.com/c16.shtml) was spot on for me, and that is what we went for.
I called various eye docs to find one that has and would help me with shooting glasses.
For some of you who NEED glasses like me, I have a recommendation.
Use a regular frame with shooting prescription in the sighting lens, but for the other eye, a bifocal (distance to walk around with + reading to see the stuff on the bench).
GaryN wrote:For some of you who NEED glasses like me, I have a recommendation.
Use a regular frame with shooting prescription in the sighting lens....
Depending on your stance, prescription and frame that could be very bad news. You need to be looking squarely through the optical centre of the lens, at your sights, in your normal shooting position.
If you can achieve that with a regular frame then fine, if you can't then you will be making problems for yourself.
For some of you who NEED glasses like me, I have a recommendation.
Use a regular frame with shooting prescription in the sighting lens, but for the other eye, a bifocal (distance to walk around with + reading to see the stuff on the bench).
The website is in German, select "Produkte" the "Brillen" on the drop down. The item of interest is the "Shooting Star" frames that combine cutaway prescription lenses with a separate shooting lens. Maybe of greatest use to the fullbore rifleman who needs to aim, read the sight vernier, watch the wind flags and write in his scorebook.
It never ceases to amaze me that people will spend $0000+ on their pistol / rifles and yet get squeamish and spending a couple of hundred on their eyes!
Remember watch your sights! (Oh and be able to see them first)
Julian
I have to smile at your statement, cuz that was my problem, my front sight was just a blur and I just could not focus on it, and I would get a headache trying to.
Rutty, that is why I have to do what I did.
I can't read stuff on the bench (like my notes) w my shooting prescription, so I need the reading prescription.
And I can't see distance, so I need the distance prescription so I won't fall over from getting dizzy w the world being out of focus.
At least w AP I'm pretty much looking straight at the rear sight.
With AR until I was taught to cant the rifle, I was looking out of the upper left corner of the lens. It still isn't center but closer.
I actually got a shooting glasses frame, then after working w my eye doc realized all the other issues my eyes have. So my Varga frame sits unused. Although I did think about putting another lens on the Varga (or another) frame and making that one a bi-focal lens.
While I will agree that it is good to 'concentrate' on the front sight in the mental sense, you do not want to 'focus' on the front sight in the optical sense.
Shooting is really more akin to photography that usual eyesight, in that it is the only use of the human eye I can think of where you are actively trying to focus on two objects at a time, and therefore need to manage your depth of field.
The correct technical answer is that you want your relaxed focus to fall at a point that is between your sights and the target, such that your depth of field is centralized between them. This allows the sights to fall in 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. This magical distance that is half way between the two is called the hyperfocal distance of the sight, and is almost independent of the distance to the target (as all targets fall at nearly optical infinity).
The actual value of the lens to use is most often +0.75 diopters added to your distance prescription for a pistol, and +0.50 diopters added for a rifle. In a pistol this will balance your focus between the rear sight and the target, which means your front sight will be slightly sharper than either the rear or the target.
Small apertures on your glasses will improve your depth of field, and will sharpen focus on everything, including reducing the effect of an uncorrected astigmatism, but the best solution is to just fix the astigmatism with a lens.
The math of diopters is shockingly simple. Assuming you start with distance corrected vision, the diopter value is simply the mathematical inverse of a lens focal length in meters. a 2 diopter focuses at 1/2 meter, a 3 diopter at 1/3 meter. A 0.5 diopter will focus at 2 meters.
The hyperfocal lens power you need is simply the average of the lens you need to see the front sight and the lens you need to see the target. A 10m target requires a 0.1 diopter lens, a rear sight that is 24" (0.6 meters) from you requires a 1.66 diopter lens. The average of the two is a 0.88 diopter. Lenses come in 1/4 steps, and you always round down, so you want a +0.75.
For a rifle with a 1 meter front sight you need a 1 diopter, if the target is at 100meters you need a 0.01 for the target. The average is +0.50.
For many shooters you do NOT want to be able to focus on the target at all. No how, no way. The target isn't going anywhere, but your sights are. There is a strong temptation to look at the target and lose concentration on the front sight. That's a great way to shoot a lot of bad shots.
My lenses are set up so the target is always blurry, but I can see my front sight just fine. If you read the majority of books on pistol shooting, the first thing they will tell you is NOT to focus on the target. Setting up your lens so that is easy to do is asking for trouble for a large number of shooters.
ShootingSight wrote:While I will agree that it is good to 'concentrate' on the front sight in the mental sense, you do not want to 'focus' on the front sight in the optical sense.
Shooting is really more akin to photography that usual eyesight, in that it is the only use of the human eye I can think of where you are actively trying to focus on two objects at a time, and therefore need to manage your depth of field.
The correct technical answer is that you want your relaxed focus to fall at a point that is between your sights and the target, such that your depth of field is centralized between them. This allows the sights to fall in 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. This magical distance that is half way between the two is called the hyperfocal distance of the sight, and is almost independent of the distance to the target (as all targets fall at nearly optical infinity).
The actual value of the lens to use is most often +0.75 diopters added to your distance prescription for a pistol, and +0.50 diopters added for a rifle. In a pistol this will balance your focus between the rear sight and the target, which means your front sight will be slightly sharper than either the rear or the target.
Small apertures on your glasses will improve your depth of field, and will sharpen focus on everything, including reducing the effect of an uncorrected astigmatism, but the best solution is to just fix the astigmatism with a lens.
The math of diopters is shockingly simple. Assuming you start with distance corrected vision, the diopter value is simply the mathematical inverse of a lens focal length in meters. a 2 diopter focuses at 1/2 meter, a 3 diopter at 1/3 meter. A 0.5 diopter will focus at 2 meters.
The hyperfocal lens power you need is simply the average of the lens you need to see the front sight and the lens you need to see the target. A 10m target requires a 0.1 diopter lens, a rear sight that is 24" (0.6 meters) from you requires a 1.66 diopter lens. The average of the two is a 0.88 diopter. Lenses come in 1/4 steps, and you always round down, so you want a +0.75.
For a rifle with a 1 meter front sight you need a 1 diopter, if the target is at 100meters you need a 0.01 for the target. The average is +0.50.
Art
well, that's one person's opinion; though posting it over and over apparently makes it more valid for pistol.
