eye relief

[JPK]

Attached is a image of a good sight picture . My question is eye relief(area around front globe sight) is this the eye relief that most everyone should be close to?

[23's Dad]

I'm somewhat interested to read different views on this topic.

My mental image of my sight picture is: The ring in the element of my front site is crystal clear. The target is a little fuzzy. I don't know what is outside the tunnel, and am only vaguely aware of the rear sight aperture. I'm looking for that front ring to hover around my target without any muscular inputs from me (i.e. tension in the shoulder). I've always believed that the eye will naturally center the front sight. Basically I have tunnel vision on the inner circle. I can't remember every really seeing the three circles and the disk in the image. I know they are there, and I can see the foresight tunnel as I am getting into position and checking my NPA, but once I place my finger on the trigger - that all vanishes. I see one circle and one disk.

Maybe I'm too tunneled? What say you all?

[Martin H]

I see about the same amount around the front sight.
Martin

[redschietti]

I check that front is centered. Check that level is correct then just focus on front sight/bull. Im not a world class shooter tho!!

[Hap Rocketto]

JPK,

I think you are using the wrong term in your question.

Eye relief is the distance from the rear aperture and your eye. It is the point at which the your eye obtains the full viewing angle. It changes from position to position, closer prone than in standing, but is usually about two to six inches.

23's Dad and redschietti have a good handle on your question. You are concentrating on the front sight and the bull's eye and the rest sort of disappears. All three elements, rear aperture, front sight, and bull's eye, are circles and circles tend to center on each other.

Regards,

Hap

[KennyB]

Like Martin, I try to have about the same amount of gap around the outside of the foresight tunnel.

One of our top "ex-shooters/now coach" recommends the gap around the foresight tunnel to be about equal to the width of the foresight tunnel - so "1/3 gap : 1/3 foresight : 1/3 gap".
These proportions can require different eye relief (distance from eye to rear iris) for different light levels (i.e. indoors where the light levels are hundreds of lux - to outdoors where they are thousands of lux).

Increasing the eye relief will make it easier to center the foresight tunnel in the rear iris (as there is less gap around the foresight) but the clear "sweet spot" in the center of the rear iris will be smaller and you may get some distortion of the foresight element depending on how old and knackered your cornea/lens are.
Decreasing the eye relief does the opposite - harder to center the foresight tunnel but larger sweet spot for the foresight element.

As with all these things, your eyes may be different from my eyes and your optimal sight picture might be different from mine (or anyone else's) - so some (much) experimentation is called for to find the best compromise.

K.

(Usual disclaimers apply - advice is worth what you pay for it, I reserve the right to be wrong & these opinions may change.)

[JPK]

Ok I guess to need give more info. I coach junior athletes. I seen the posted image of a sight picture used by Walther air rifles. It got me thinking I am 90% sure that the rear iris used on the rear sights we have do not allow that much space or light around the front sight globe assembly. In general we like to see athletes use a 3.8mm - 4.2mm front aperture on the front sight to allow for plenty of space and light around the bulls. What about the space and light around the entire front globe. Yes we mostly concentrate on the front sight, but we still need to center the front globe in the rear sight. We do not have adjustable rear apertures so I have adjusted the "eye relief" by bringing the rear sight as close as i can to the rear, and at least through my eyes I do not get anywhere near that amount of light and space around the front globe. So i ask the question to determine if i need to drill out the size of the hole in the rear sights to get something closer to what the picture looks like.
Thanks

[23's Dad]

We do not have adjustable rear apertures so I have adjusted the "eye relief" by bringing the rear sight as close as i can to the rear, and at least through my eyes I do not get anywhere near that amount of light and space around the front globe. So i ask the question to determine if i need to drill out the size of the hole in the rear sights to get something closer to what the picture looks like.
Thanks

Drilling the aperture will have the same effect as opening the aperture on an adjustable rear. I don't think it will increase the area you see significantly. It will reduce the depth of field and cause your target to be less distinct. Younger eyes than mine may not have as difficult time as me, but opening the aperture overly large doesn't help my sight picture.

[KennyB]

Drilling the aperture will have the same effect as opening the aperture on an adjustable rear. I don't think it will increase the area you see significantly. It will reduce the depth of field and cause your target to be less distinct.

This is correct.
With a variable rear iris, opening the iris up doesn't alter the gap you see between the foresight and rear peephole.
Drilling the rear aperture is not going to be the solution and it's irreversible.
If you've brought the rearsight back as far as it goes and there still isn't enough space around the foresight tunnel then you are going to have to either bring your head/eye closer to the sight (shorten the butt possibly) or look at some kind of rearward extension like this:



K.

[JPK]

I thank you all. That is exactly the kind of feed back I was hoping for. So back to original question. Is that the amount of space to try to achieve?

[abinok]

Conventional wisdom is that the front sight housing should fill around a third of the field of view. What sight are you using? Which rifle?

[Humpers]

With a variable rear iris, opening the iris up doesn't alter the gap you see between the foresight and rear peephole.

Please could you explain why this is the case, as it seems to be counter-intuitive.

Many thanks.

[KennyB]

With a variable rear iris, opening the iris up doesn't alter the gap you see between the foresight and rear peephole.

Please could you explain why this is the case, as it seems to be counter-intuitive.

Many thanks.

Hi Humpers, it does seem counter-intuitive doesn't it. I wish I could explain it definitively but my knowledge of optics is a little rusty.
I'm guessing that it's to do with the peephole being significantly smaller than the pupil of your eye - as changes in the dilation of the pupil due to changes in light level DO make a difference, as does changing the distance from the peephole to your eye.
I urge you to try it for yourself - open up your rearsight and watch how the "gap" between the foresight and the perceived edge of the rear iris doesn't change... Then set the iris back to around 1.1mm, close your non-aiming eye and see if the peephole shrinks - especially on a bright outdoor range

K.