Rifle Scopes Optics for the Nearsighted

[BytorJr]

Ok, that's just a "catch phrase" as I know they don't make optics for us nearsighted folk.

However here is my question, and had I listened to "Rabani" in Physics II I probably would know this. I've noticed this:
1) Red dot (MRO, Aimpoint, Athlon, etc) the dot is BLURRY (actually 2 dots) because I'm nearsighted with just a very small amount of astigmatism (not worth correcting due to headaches correction gives). I put my glasses on, boom, clear as a bell.

2) Scopes: exactly the opposite. Glasses on I'm fighting the damn glasses and generally cannot see shit.

3) EoTech - haven't tried this recently, but I'm going to guess it's kind of in-between. I never sent mine in (found out too late) for the recall - old N-cell one. I don't recall any blurriness with an EoTech.

So, somebody with optics background can answer this...maybe the Dark Lord .

1) I'm assuming that the reason I have to wear glasses on red-dots because the focal point is actually the target 25-200 yards away where I actually need correction to see well (with my dominant eye...week eye is farsighted but a fair bit of astigmatism).

2) On a scope, the focal point is somewhere "in" the scope which plays to the strength of my nearsightedness.

Or am I completely nuts and crazy here?

Thanks.

 

[mick243]

on the scope, the diopter setting will be vastly different between glasses on and glasses off.

I personally find it better to adjust the scope to my eye without glasses, but I know other people who just cant get the scope adjusted right unless they are wearing glasses (probably something to do with what kind and how much correction) and I know of some people who have their glasses correction ground onto a lens that they connect somehow to the eyepiece of their scope (unsure of the full details, might be replacing the eyepiece or just adding an extension with the extra lens, but whatever, you need t do what works for you). yet other people have a special set of glasses made with the scope in mind (ie, they might have a set for driving, a set for reading, a set for the computer and a set for shooting all with different corrections - it might pay to take your scope to an optician and ask for a set of lenses to work with it)


so for 1) no idea, never used a red dot.... not an optical specialist either

but for 2), yes the focal point of your eye looking through your scope is wherever the eyepiece focuses it inside the scope (the second focal plane I think)

 

[308pirate]

Don't you people wear corrective lenses?

I have myopia (a LOT of it), astigmatism, and presbyopia. I wear corrective glasses 24/7. They are my normal correction, and I don't use any special glasses to shoot with.

All my red dots are round and crisp. I have zero trouble shooting anything with optical sights.

I don't understand why so many get wrapped around the axle over this.

 

[6.5SH]

For RDS I prefer to use absolute co-witness and use a flip-up rear aperture if shooting at a distance that I need to refine the dot down to its correct size and sharpness.

For magnified optics I adjust the diopter for reticle focus without glasses and will shoot matches without corrective lenses.

Ideally I should get actual prescription shooting glasses with large enough lenses to accommodate different viewing angle and the optical center ground closer to the top of the lens where you would normally be looking through when shooting ($$$).

 

[BytorJr]

Don't you people wear corrective lenses?

I have myopia (a LOT of it), astigmatism, and presbyopia. I wear corrective glasses 24/7. They are my normal correction, and I don't use any special glasses to shoot with.

All my red dots are round and crisp. I have zero trouble shooting anything with optical sights.

I don't understand why so many get wrapped around the axle over this.

I'm not actually wrapped around the axle. . As all of my eye doctors have said "you're perfectly blind and have figured out how to game the system." So for me, if I'm shooting RDS I wear my corrective lenses; but behind a scope, I just put my safety glasses on and I'm pretty much good to go. IF (or should I say WHEN) I have to go to bifocals (I'm at slightly less than a 0.5x reader according to doc, so no reader glasses needed) then I suspect I'll not be able to pull of the trick of take corrective lenses off and play.

So my question of the focal point I think was answered. When I'm focusing using a scope, I'm actually focusing on an area "in" the scope whereas because a red-dot has pure 1x, I think I'm focusing at the actual target.

I'm sure Ilya can more eloquently and accurate explain this from an optics standpoint. It works for me, but I was more interested in the physics. (snort snort snort).

 

[Hesperidins]

Don't you people wear corrective lenses?

I have myopia (a LOT of it), astigmatism, and presbyopia. I wear corrective glasses 24/7. They are my normal correction, and I don't use any special glasses to shoot with.

All my red dots are round and crisp. I have zero trouble shooting anything with optical sights.

I have the same eye conditions and recently started wearing multifocal contacts. For me, I've always worn contacts when shooting. I've never worn my glasses, not once. Anyway, I don't have any problems. I only have traditional scopes, no experience with red dots.

 

[Denys]

I have been wearing glassed for over 50 years but not 24/27; I don't wear them when I sleep or take a shower, etc.

The subject of eyeglasses and riflescopes is a little bit complicated and somewhat specialized, and it's very dependent on the individual. Here are a few things to keep in mind.

1- The riflescope ocular is an afocal device that projects the picture at the rear of the erector assembly to the pupil of your eye. Afocal means that it does not focus the image, your eye does that by focusing the parallel rays coming from the eyepiece.
2- The diopter is a measure of the optical power of a curved lens. The diopter is the reciprocal of the focal length measured in meters. A diopter value of 2 would focus the rays at 1/2 meter. A flat window has a diopter value of 0, which means that it is not focusing the parallel rays anywhere. A sure way to understand all this is to look at your prescription. There should be a value for each eye and for nearsighted folks like me, that is a negative number for each.
If I look at my glasses I see that they are curved out a little bit. That's a negative diopter value meaning that I am mildly nearsighted, with a prescription of about -1.5 diopters.

Now, for some reason my arms have gotten shorter over the last few decades and I can't hold a book far enough to read it properly. To counteract that, the optometrist adds a diopter of about +2 at the bottom of my lens so these are not following the same curve as the top of my glasses, they actually flatten out. Corrections are additive, so -1.5 and +2.0 actually work out to +0.5 for reading. As it works out, if I keep my glasses on to look through a riflescope, I can leave the diopter adjustment at or near 0. That's a corrected eye.

On the other hand, I prefer to shoot without my glasses because of various issues, one of which is that my reading prescription is at the bottom of my glasses, not the top and I have difficulty adjusting to that. Also, in Texas it gets hot and sticky and glasses fog up really quick. So I remove my glasses and adjust the diopter of the eyepiece to my uncorrected eye, which works out to about +0.5 diopter for a clear and crisp image.

Eyepieces have corrections that usually from -2 to +2 diopters or something similar. The important part for the shooter is the near prescription (a + number for presbyobia). If you do not need bifocals, that means your corrected eye is able to focus properly for near objects and the diopter can be at 0 on the eyepiece. If you do have bifocals, that's where it gets tricky. You need to find out what your prescription is (something like "-1.5 add 2") and then you need to set the diopter to what that added value is, in this case, +2.)

I hope that clears it up for you.

 

[OutThere]

Don Nygord, (in his Nygord's Notes) and Dr. Norman Wong have published some great info on vision and competitive shooters. Worth a read.

 

[SepticDeath]

Don't you people wear corrective lenses?

I have myopia (a LOT of it), astigmatism, and presbyopia. I wear corrective glasses 24/7. They are my normal correction, and I don't use any special glasses to shoot with.

All my red dots are round and crisp. I have zero trouble shooting anything with optical sights.

I don't understand why so many get wrapped around the axle over this.

Agreed. I am 42 and have been wearing glasses and contacts since I was 10. No problem with optics either myself.

 

[TheOE800]

Don't you people wear corrective lenses?

I have myopia (a LOT of it), astigmatism, and presbyopia. I wear corrective glasses 24/7. They are my normal correction, and I don't use any special glasses to shoot with.

All my red dots are round and crisp. I have zero trouble shooting anything with optical sights.

I don't understand why so many get wrapped around the axle over this.

I have astigmatism, but do not wear corrective lenses due to laser surgery. I have no real need for correction anymore yet my astigmatism remains.