Whale oil beef hooked! A breakthrough, I can see again ...

[Patrick Chadwick]

What follows is a simplifed explanation that is not scientifically exhaustive, but adequate for present purposes...

No-one of mature years is going to be able to see backsight, foresight and target all clearly at the same time, so you have to make a choice.

The one element you must see clearly is the foresight - whether blade or ring. If you have an aperture backsight, this is usually so close to the eye that a) not even a teenager with 20-20 vision can focus on it and a foresight simultaneously, and b) it is not necessary to focus on the backsight, as the eye naturally tends to center in the fuzzy aperture. Conscious control to make sure that the field of view really is central, and not just accidentally so, is the clue to better aiming with an aperture backsight (and for telescopic sights as well).

So the lens for shooting with an aperture backsight is optimized so the the depth of field (the range over which everything appears adequately focussed) has the foresight as the near point and the field extends out towards the target, without any attempt to get the backsight aperture in focus.

Of course, the depth of field is also dependent on the aperture. The depth of field increases as the aperture is stopped down. So the optician checks the setup with the maximum size of aperture you are likely to use in practice, and if the light enables the use of a smaller stop, the depth of field will be even larger.

With an open backsight the adjustment must be different. There is no automatic centering trend, as with an aperture backsight. So the foresight is taken as the far point, with the depth of field extending back towards the open backsight. Once again, the depth of field is increased by stopping down the optical aperture, which is why those spectacles with a grid array of holes produce a sharper picture with open sights. But a better solution is to have an adjustable iris on the shooting glasses, so that the aperture can be reduced as far as the light permits.

Please note that you cannot shoot well with an aperture backsight combined with those hole-grid spectacles. The aperture backsight is both the optical stop and an aiming reference. An additional aperture behind, whether as an iris or the hole grid can only act as a stop and increase the depth of field if it is optically smaller (i.e. subtends a narrower angle at the eye) than the backsight aperture. Which means that you lose the aiming reference of the backsight aperture. So the iris/hole grid element is only for shooting with open sights!

You will also have noticed that the best solution actually requires two lenses - one for shooting with an aperture backsight, and one for shooting with an open backsight.

The optican who made my shooting glasses has a well-deserved national reputation. He examined my eyes with equipment of a sophistication that I have never seen in an ordinary "downtown" optician's room.

I had wondered for some time why I had a marked tendency to produce double groups, separated vertically by a couple of MOA, even when shooting off sandbags when I could be pretty sure that an unconscious shift of hold was not the explanation.

He (or rather his equipment) was able to detect a flaw in my right eye that causes a double refraction. I literally see double in the vertical direction. The second image is that ominous couple of MOA above the "true" image, and much weaker, but strong enough to allow a false aim if I am not careful. This flawed region is about 1 mm below the center of the iris, so although I wrote above that one should make sure that the eye is looking through the center of any aperture, in my case I can improve the picture by deliberately looking low, so that the defect area is out of the sight line. With this insight, I have been able to vastly improve my aiming capability with open sights by learning to hold the blade very deep in the backsight, almost to the point where it disappears.

Ten to one AM here now!

G'night!

[Baal]

Getting some good info here. Luckily, though my eyes are aging fast, I don't much of a problem aiming yet.

One thing I'm not clear on. Do these shooting glasses with the iris also have a lens? Or is it just an iris?

[Patrick Chadwick]

Do these shooting glasses with the iris also have a lens? Or is it just an iris?

Both:
1) lens for shooting with aperture backsight
2) lens + iris for shooting with open backsight

So I have 3 attachments for the frame of the shooting specs. As it was irritating to keep on swapping lenses (you have to make sure every time that the lens is square-on to the aiming line) I later bought a second frame, so I now have 2 shooting spectacles and don't have to keep on swapping the lens.

If your eyesight is better than mine, you may be able to manage with 1 set of spectacles and 1 lens, with a clip-on iris for shooting with open sights. But the very first requirement is an optician who really knows about shooters' requirements. The optician who made my lenses does not rely purely on the optical diagnosis and measuring equipment, as sophisticated as it is. His premises include a very long cellar with carpeted floor + targets where you can test-aim the lenses with your own rifle(s) - and even has a couple of rifles with open sights and aperture sights for you to use when fine-tuning the lens prescription.

As I wrote earlier - an eye-opening experience! It was only when I tried out the lenses with my rifles in the optician's cellar that I fully realized how poor my eyesight had become for shooting.

Patrick

[jmoore]

Maybe I ought to get a new passport...No eye doctors like that around here!

[Baal]

yeah, I've got to wonder if there's an optician anywhere in Canada who knows about this stuff. I've got my annual eye exam coming up in a couple weeks so I suppose I'll just ask if they know of any.

[Patrick Chadwick]

I can only repeat and recommend - get in touch with small-bore competition shooters. The competition is so severe that they have all these subleties sussed out!

[burgie]

Hello folks, found this at Brownells.

LYMAN : HAWKEYE SHOOTERS OPTIC AID - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools - BROWNELLS

[RJW NZ]

Thats probably the perfect answer for iron sights!

[paulseamus]

Just to add my two cents worth.

I have crappy eye sight but a damm good optican, Nigel Chesterfield-Evans, who has set me up with a pair of Champion shooting glasses for shooting my iron sighted No 111* and No4 mk2.

I am short sighted in both eyes and my right eye is also affected by astigmatism.

Two key issues that Nigel has helped me indentify and fix.

The first is that my normal glasses distort the natural image seen through the right lense. As my focus moves from the center of the lense towards the left or right edge, the image through the lense lappears further left or right than it actually is. (try looking at the edge of you monitor through the top half of your glasses and see if the image above the lense lines up with the image below the lense. Then whilst looking teh the same spot see how this changes as you rotate your head slightly left to right,)

The second issue is that when maintaining a normal check rest position, my line of vision/aim was through the left half of my lense resulting in the distorted image described inadequately above.

The champion glasses addressed both issues by allowing the lense to be positioned so that my line of vison/aim is always through the centre of the lense whilst maintaining a normal check rest and by ensuring that the lense is also square to the line of sight.

Getting the lense positioned correctly involved me taking my rifles in to the Optometrists store and Nigel carefully adjusting the lense position whilst I sighted the rifle down the corridor --- I would like to take the opportunity to apologise to the sweet old lady who walked in unexpectedly and thought I was holding up the store

Has my shooting improved? Only a bit......but at least I can see clearly when I miss and I can now move on to addressing other issues with my technique. i.e breathing, flinching, the list goes on.... and on.

Happy days

Paul

[Patrick Chadwick]

Guys, this is the sort of stuff you should be looking for:
http://www.gehmann.com/pages-en/prod...20frames&id=11

or this
http://www.gehmann.com/pages-de/deta...&headline=Zoom

I have one of these, for attaching to normal spectacles
http://www.gehmann.com/pages-de/deta...&headline=Zoom

It's all out there somewhere - you just have to look!

The first is that my normal glasses distort the natural image seen through the right lense.

And if you can cope with the German, this will help you to understand why your normal spectacles are NOT the best to use for shooting.
http://www.mueller-manching.de/warum.htm

Take a look a the young lady with the air pistol. The first following pic is what you get with your driving glasses. The second pic is what you get with customized shooting glasses.

Now take a slow look at this page. I said a SLOW look - the second pic is dynamic, and shows how your normal glasses screw up your sight picture.
http://www.mueller-manching.de/skoffen.htm

There is a lot on this site. More than I have found anywhere else on "the vision thing" for shooters.

And just in case anyone with a nasty suspicious mind (like me!) is wondering: I am NOT getting a percentage from Mr Müller. I do NOT have shares in the business. I am just a satisfied customer! Now go find something like that in your home country!

Patrick