TargetTalk

ShootingSight wrote:The math I proposed is exact and infallible, in that it represents the offset between a perfect infinity focus, and a focal point where your depth of field is centered between the sight and the target, giving you relatively the same focus on both. You don't get to violate laws of nature.

What is slightly less precise is where your eyes focus when they are totally relaxed. Most people who are 20/20, but are just presbiopic will focus close enough to infinity that the +0.75 for pistols and +0.50 for longer rifles is what you need. However there are also some people who focus near, but not at infinity, so they might find their ideal lens is 1/4 diopter off.

Bottom line, you want an optometrist to give you a distance measurement. Ideally, you want it done while dilated, and you want it done to a 1/8 diopter sensitivity. Then you can add the optical math I outlined.

The other option is to ask the eye doc to put an eyechart at 2x the distance to the rear sight, and obtain your best focus at that point. For most people, that is close to 48 inches away, because you hold your pistol so the rear sight is about 24 inches from you. Obviously, arm lengths vary slightly, but since lenses need to be rounded to the nearest 1/4 diopter, minor variations get washed out.

Insert deep sigh here!
The maths might be exact and infallible, but the premise when applied to ISSF pistol is open to question.

Many thanks, Shootingsight. I am due my annual physical. I think I'll take my air pistol with me (military clinic) and see what I can work out with the optometrist. The Army pays for one pair of glasses per year. I'll let this one be the one.

Spencer wrote: Insert deep sigh here!
The maths might be exact and infallible, but the premise when applied to ISSF pistol is open to question.

Spencer,

could you elaborate please? I ask as a rifle shooter, where a lens does help even at a weak prescription. What is different about pistol?

Tim S wrote:

Spencer wrote: Insert deep sigh here!
The maths might be exact and infallible, but the premise when applied to ISSF pistol is open to question.

Spencer,

could you elaborate please? I ask as a rifle shooter, where a lens does help even at a weak prescription. What is different about pistol?

I won't attempt to answer for Spencer but, IMHO, it's nowhere near as cut and dried as "pistol shooters need +0.75".

For the first 25 years (or so) of my 34 year shooting career, with a normal prescription of between -6.00 and -6.50, I was not able to handle +0.75.

+0.50 worked MUCH better for me.

Now that I'm approaching middle age (I wish) +0.75 works.

I would say that in all that time I have used the same shooting frame with the same eye relief.

The "+0.75" has been quoted so often that it has become an urban myth with pistol shooters. Good to see some of the "older" and experienced pistols shooters have widened the scope.
I am 70, and have previously had shooting prescriptions made by non-shooting optometrists. Generally made an improvement, but not perfect. Recently I located an optometrist who also shoots. I had prescriptions made for my free pistol and S&W revolver. They both worked great, but when I went to use my standard pistol, couldn't get a clear front sight with either lens. We are now working on making a prescription for this pistol. 3 pistols of different lengths, 3 prescriptions of different strengths.
The optometrist has noticed that this is common for older people who often need more than 1 prescription. Where a single lens will work when you are younger, as the eyes are less able to accommodate and adjust as you get older the situation changes.
There are other factors which will affect your sight picture, but this is a starting point. The key is to find an optometrist who is also an experienced shooter, understands all the variable involved, and take your pistol with you when you have your eyes tested.

Tim S wrote:Spencer,

could you elaborate please? I ask as a rifle shooter, where a lens does help even at a weak prescription. What is different about pistol?

ground rule - discussion related to ISSF Pistol/Rifle

for ISSF rifle, the shooter is concentrating on concentricity of the aiming mark and the front aperture: seeing both (reasonably) well focussed has application and the hyperfocal solution can work well.

for ISSF pistol, a number of other factors come in to play. In no particular order:
- the comparatively gigantic wobble area (standing position, one hand only),
- the comparatively large scoring rings,
- open sight elements,

All up, a good solution is:
- to accept the wobble area (while working on reducing it),
- take maximum advantage of the size of the scoring rings and take the 'leap of faith' and use area aim, and
- allow your 'subconscious' to take care of alignment between the sight elements - i.e. concentrate at and on the front sight and let you 'subconscious' take care of the alignment of the sight elements.

There are procedures that show that for the vast majority of shooters who accept area aim, the best procedure returning small groups from the shooter/equipment combination is to focus at, and on, the front sight.

Applying the hyperfocal procedure to ISSF pistol can have some shortcomings:
- it encourages shooters to 'check' the target by focussing at it while firing a shot,
- it can lead to eye-strain during a precision event or stage if a shooter (particularly if 'older') ranges the focus distance.

Hope this simplification helps...

Thank you Spencer.

Having shot AP very badly on a few occasions, you'd think I would remember the wobble!

In addition to what Spencer says, I'll add that as a shooter you need to see what works best for you in acheiving the objectives - i.e. a clear foresight. The pure maths approach may be right for you, but it isn't a given.

I should add that I use an identical prescription in both my rifle and pistol glasses and that appears to work well for me.

Rob.