Vision Issue

[ModestoPete]

I am shooting FP at 50m and AP at 10m on the same outdoor range right after each other.

The lighting is similar with just a slight change due to time.

I use Knobloch glasses with a 1.00 lens for FP. However, if I use the same for the AP, I have trouble keeping my eye from going to the target.

Is this common? Should I use a stronger lens for AP? Should I use a tint?

Any recommendations?

[LukeP]

to get back to the sight, at least you can slighty reduce your correction, so you focus near the sight and less towards the target.

[Gort]

I have to use .25 diopter more power to focus on AP front sights because they are closer to the eye. You are shifting to the target because the sights are not in crisp focus, try 1.25 diopter and see if that corrects your problem.
Gort

[ModestoPete]

The distance from my eye to the front sight of both my AP and FP are about the same distance, 36".

Is it that the target is so much closer in AP that I am looking at it?

[trinity]

Are there such things as diopter clipons (for Knoblochs)? This is something I've wanted to experiment with.

I am far sighted, so what that means is, given a sufficient amount of time, my eyes will adjust to anything.

I tried the VarioLens in front of my prescription (to correct the astigmatism), but the clarity of the Variolens is not good enough.

I have all sorts of colour filters for the Knoblochs, but are there 1/4 diopter clip ons?

-trinity

[Spencer]

I am shooting FP at 50m and AP at 10m on the same outdoor range right after each other.

The lighting is similar with just a slight change due to time.

I use Knobloch glasses with a 1.00 lens for FP. However, if I use the same for the AP, I have trouble keeping my eye from going to the target.

Is this common? Should I use a stronger lens for AP? Should I use a tint?

Any recommendations?

if you are shooting at 10m outdoors in daylight (? see 3.5.1.3, 6.4.1.6) your depth of field could almost stretch to 10m; making the distraction of the target more noticable.
If shooting indoors to ISSF light requirements for 10m ranges the depth of field from 1m (the front sight) will not include 10m (i.e. the target line).

- stronger lens will only make your eye muscles get tired sooner
- tint could make a reduction to the depth of field if your iris enlarges to cope - the colour won't make a difference, but the reduced light transmission will
- brain work needed... front sight, FRONT SIGHT, FRONT SIGHT, etc.

[Rover]

At the moment I'm experimenting with not using the iris on my glasses. It's a little distracting and I think, because it makes the bull sharper, that it might be causing me try to "ambush the bull" occasionally.

This has made the bull fuzzier, but has not made any difference in my scores. I'm still working on this to see if anything changes.

In the short time I've been practicing this way, I seem to notice fewer really bad shots. But....

Both Steve Reiter and John Zurek have called my attention to the problem of lack of focus (mentally) as one gets older. Naahh, couldn't happen to me!

[j-team]

Both Steve Reiter and John Zurek have called my attention to the problem of lack of focus (mentally) as one gets older. Naahh, couldn't happen to me!

Hang in there, you can still remember their names at least!

[shadow]

I am farsighted with a pretty strong plus prescription - something like a +5. I have noticed the same thing as the original poster. My Knoblochs have two positions or holes for the right lens. I thought about experimenting with the two different holes - possibly using one for 50m and one for 10m.

[RobStubbs]

Your focal point should be set just in front of the foresight - which is the same for free or air, so I'm not quite sure why you think you need a different prescription. A diopter increases depth of focus as you step down the hole size, which can be a disadvantage. The whole point of a lens is to enable you to easily focus on the important bit, i.e. the front sight. A diopter encourages poeple to switch between target and rearsight, hich is counter productive. The only other comment I can think of is that light is far greater outdoors than inside. That makes your pupil contract which again increases the depth of focus. Most people appear to find it easier outdoors seeing the sight picture in free than they do indoors for precisely that reason.

Rob.

[rmca]

- brain work needed... front sight, FRONT SIGHT, FRONT SIGHT, etc.

I would start with this before making any other adjustments. You could try a training session just dedicated to this point.

I've struggled with this in the past (and some times in the present). What I find helping is making a conscious effort to set your eye on the front sight and don't let it escape to the target.

As Spencer said, "brain work needed"

[Rover]

What Rob said is perfectly correct. This does not mean that you don't need to change your glasses. I'd try to find an eye doctor who works with shooters.

[slofyr]

...Both Steve Reiter and John Zurek have called my attention to the problem of lack of focus (mentally) as one gets older. Naahh, couldn't happen to me!

[ModestoPete]

Yes, I am not sure that my prescription was ever correct.

Thank is why I have scheduled an appointment with Dr. Norman Wong in San Francisco.

http://www.starreloaders.com/edhall/nwo ... guide.html

He has written an number of articles which are very enlightening.

http://www.starreloaders.com/edhall/nwongarts.html

[ShootingSight]

There is a lot of misinformation, or misunderstood information out there, let me set a few things straight.

The goal for a pistol shooter is to adjust your focus so your depth of field is centralized between the rear sight and the target. This will result in the front sight being slightly more sharp than the target. To do this, you want your focus to be at what is called the 'hyperfocal' distance of the rear sight. The optical math is not complex, but the bottom line answer is that you likely want +0.75 diopters added to your distance vision correction. I'd say in 95% of people I have worked with, this simple math gets you to the best solution.

The fact that you use a +1.00 and still have trouble seeing the front sight means that you are slightly far sighted, so there are a few possible paths forward: go to the eye doc, and take your distance prescription for the shooting eye and add +0.75 to the sphere value. Cheaper is to try a +1.25 lens. Luckily for you, this happens to be the power of standard reading glasses, so go to Walmart and get a set of $10 reading glasses that are +1.25. Beware that these are NOT impact resistant or safety glasses, but they do serve as good try outs. I recommend buying them and taking them home to test - taking your gun to Walmart will create a scene. If your eye still wanders to the target, go to a 1.5.

You will tire your eyes by using a lens that is too weak. You will NOT tire your eyes by using a lens that is too strong. With a weak lens, your eye can still exert the ciliary muscle to pull the focus in closer, so the lens is doing part of the work, your eye is doing the rest. The eye muscle is an unopposed muscle, so while you can exert to pull focus in, if you use an excessively strong lens, your eye cannot push focus further out, so once the eye muscle is fully relaxed, it can't relax more. So your goal here is to use as strong a lens as possible. If you use a too strong lens, what you will see is a sharp front sight, and the target will be blurry, no matter how hard you try to look at it. Generally, the way a doc would test you is to start with an overpowered lens, and then slowly back down the power. When you get to the point where the target is as sharp as the front sight, even if you TRY to stare at the target, that is your perfect lens. Your eye is getting a good sight picture while remaining totally relaxed.

For shooting, 10m and 50m are identical to your eye. From infinity, 10m represents a 0.1 diopter shift, 50m represents a 0.02 diopter shift. The smallest step a human eye can normally discern is 0.125 diopters, so the 0.08 difference between the two can not be seen.

Once the focus is set, you want to use a small aperture to increase your depth of field. In some places, this small aperture is referred to as a diopter, so be aware that it can create confusion between diopter which is a metric measure of lens strength, and diopter which is a small aperture. Here smaller is better, as it will increase your depth of field, but if you go too small, the image gets dim.

Art Neergaard
ShootingSight LLC
www.shootingsight.com

[Spencer]

There is a lot of misinformation, or misunderstood information out there, let me set a few things straight.

The goal for a shooter is to adjust your focus so your depth of field is centralized between the rear sight and the target...
etc.

While ShootingSight has an opinion that is probably applicable to rifle, for ISSF Pistol the alternative (and generally accepted) view is
Front sight, FRONT SIGHT, FRONT SIGHT, FRONT SIGHT

To achieve this, the focus needs to be at the distance of the front sight.

[ShootingSight]

No, for a rifle, you want to centralize your focus between the target and the front sight.

For a pistol, you want to centralize it between the target and the rear sight. This means that the rear edge of your depth of field will just touch the rear sight, and the front edge of your depth of field will just touch the target, so these two will be approximately equal focus.

The front sight will be solidly inside the depth of field, so it will be slightly sharper than the rear sight or the target.

If you were to focus ON the front sight, you would shift your entire depth of field towards you. The part of your depth of field that falls on the near side of your focal point would be wasted, and the target would be much too fuzzy.

If anyone wants to actually run the test, lens power (diopters) is simply the metric inverse of its focal length. I won't go into how to offset for people who wear distance glasses, but for those who do NOT need glasses to see distance, you measure the distance from your eye to the front sight. Call it 22". Convert this to metric (0.56 meters), and invert that number (1.79). That is the power of glasses you need to see the front sight in perfect focus. So go buy a set of cheap reading glasses that are 1.75 diopters, and take a look. You will see a perfect front sight, you will lose the target, and you will realize that when people said 'focus on the front sight', they were not speaking in the optical sense, and should have said 'concentrate on the front sight' .... because optically speaking (and I have sold enough lenses to pistol shooters, who had good results that this is not just some theory I am pulling out of the air), for a pistol, you want to focus at the hyperfocal distance of the rear sight.

[BobGee]

For pistol, how can you concentrate on the front sight if your focus is shifting between front sight, rear sight and target?

It seems to me that they mighty all be "in focus" with the appropriate lens but that will inhibit your mental focus.

Back again to Spencer: front sight, Front Sight, FRONT SIGHT, FRONT SIGHT, FRONT SIGHT!

[Rover]

It's simple: With your eye relaxed, your focus from your glasses should be on the front sight erring towards the target rather than the rear sight.

If the light is brighter it will easily pull your focus both ways.

[RobStubbs]

No, for a rifle, you want to centralize your focus between the target and the front sight.

For a pistol, you want to centralize it between the target and the rear sight. <snip>

If you were to focus ON the front sight, you would shift your entire depth of field towards you. The part of your depth of field that falls on the near side of your focal point would be wasted, and the target would be much too fuzzy.

I think you'll see from what's posted above, most people disagree, as do I.

The objective is to make the focal point the foresight, in both rifle and pistol. The target will be slightly fuzzy, but nothing so bad that it cannot be seen well enough to aim at - and don't forget we are only interested in seeing a black circle, nothing more.

I don't disagree that if you have the luxury, very slightly focussed infront of the foresight is ideal, but I don't believe opticians work to that level of precision.

Rob.