Adjustable Iris with a Dot

Orion · Post by **Orion** » Wed Jul 18, 2012 11:09 am

Does anyone have experience with adjustable iris' used with a dot?

Thanks.

Rover · Post by **Rover** » Wed Jul 18, 2012 1:34 pm

Why would you even consider a specialized shooting glass, much less an iris, with a Dot?

That's the beauty of a Dot, in that it requires nothing but normal eyesight (regular glasses).

But, being an inveterate tester, I'm always open to provable new ideas.

Orion · Post by **Orion** » Thu Jul 19, 2012 9:40 am

Rover wrote:Why would you even consider a specialized shooting glass, much less an iris, with a Dot?

That's the beauty of a Dot, in that it requires nothing but normal eyesight (regular glasses).

But, being an inveterate tester, I'm always open to provable new ideas.

I ran into a high master using one while shooting CF with an Ultradot. I didn't get a chance to ask him what he was getting by wearing an iris when using a dot, but he said he didn't understand why most people didn't use them.. It was probably preference.

GunRunner · Post by **GunRunner** » Thu Jul 19, 2012 9:56 am

Dots are not always round and clear to everyone, if a iris makes it clear and round then use one

Rover · Post by **Rover** » Thu Jul 19, 2012 12:19 pm

How would an iris cure astigmatism (as opposed to regular prescription glasses or lens)?

Astigmatism is what causes dots to be starry or out-of-round.

Isabel1130 · Post by **Isabel1130** » Thu Jul 19, 2012 3:58 pm

Rover wrote:How would an iris cure astigmatism (as opposed to regular prescription glasses or lens)?

Astigmatism is what causes dots to be starry or out-of-round.

It would not cure it and any magnification from the iris would make it worse.

Now if you were one of those shooters who believes that a tiny dim dot is best, maybe the iris would help you see it. An iris can also be useful to keep your head and eye aligned with the sights. However I think the more simple solution is to just turn the dot up to the correct intensity and size for conditions. I know a high master pistol shooter who says his dot looks like three dots, and a squiggle. He puts the x ring in the middle of the three dots and generally cleans the target.

JimPGov · Post by **JimPGov** » Sat Jul 21, 2012 9:42 pm

Rover wrote:How would an iris cure astigmatism (as opposed to regular prescription glasses or lens)?

Astigmatism is what causes dots to be starry or out-of-round.

THAT IS TRUE. BUT IT DOES WORK. I HAVE A SLIGHT ASTIGMATISM( NOT ENOUGH FOR A PRESCRIPTION) AND I NEVER SAW A ROUND DOT TILL I TRIED AN IRIS. JP

ShootingSight · Post by **ShootingSight** » Sun Jul 22, 2012 9:25 am

If an iris is a reduced aperture that you stick on your glasses, then it makes absolute sense that it would help with an astigmatism.

The iris effectively reduces the aperture size of your eye. The amount of blur you see on an object that is not at your ideal focal plane is driven by aperture size. Most people think of this in terms on non-astigmatic vision, where you are focused at one point, and an object nearer or further than your focal point has some blur. Reducing the aperture size will reduce the blur on these objects and is referred to as your depth of field.

However an astigmatism works the same way, where the cornea is slightly bulged into a football shape, so your eye has one focal length in one axis, and a different focal length in the other, so if you focus on the red dot with your 'good' focal length, the axis 90 degrees rotated from that will be focused at the wrong distance, and you will see blur in the other axis. Reducing the aperture increases your depth of field in all axes, so the astigmatic blur will reduce.

Interestingly, this is the principle for the rectangular apertures I sell for rifle shooters. Depth of field is directional. Blur in the vertical direction (ie on a horizontal line) is determined by how tall your aperture is, horizontal direction blur on vertical lines is driven by how wide your aperture is.

For your astigmatism, you only have blur in one direction, let's say 2 o'clock and 8 o'clock. What you could do is put two strips of tape on your glasses, with just a narrow slit of a gap between them, and you want the gap running at 90 degrees to the direction of blur, so the gap would go from 11 oclock to 5 oclock. For optometrists, this is known as a stenopaeic slit, and it gives you a small gap only in the direction you need it. This is better than just using a round opening that small, because you do not cut out as much light, so the image does not go as dim.

Now, a cylinder corrected lens works even better, which is why no one uses the slit technology.

However, this does get me thinking .... in a red dot sight, is the red dot appearing to come from infinity, so that it and the target are in perfect focus at the same time? Or do you focus at infinity, and just let the dot become slightly fuzzy?

djsomers · Post by **djsomers** » Sun Jul 22, 2012 11:03 am

I have a slght astigmatism and I just tried using an iris and it works! Dot was round as a button. My dot always looked sort of like a comet with a main body and lighter tail.

I had adjusted to the comet shaped dot though - just used the main body of the comet as my aiming point. Besides, seeing a comet is good luck.

Probably going to save my shooting glasses with iris for when I am shooting open sights.

wkev · Post by **wkev** » Fri Jul 27, 2012 7:15 pm

I had LASIK in 98 and one of the side effects for me is that I only see a nice round dot in quite bright sunshine. Cloudy day, a covered firing line, or, especially indoors, I will see multiple dots, something like the intersection graphs in math. Using an iris gives me a nice, sharp dot in all conditions.

Cheers,
Kevin Walker
GySgt, USMC Reserve Shooting Team

keith · Post by **keith** » Tue Aug 14, 2012 2:38 pm

I have astigmatizm....I use a iris always with open sights (Merit) in fact if it wasnt for the merit open sight shooting for target work would be impossible for me even with my glasses......when I shoot a dot it just depends on the dot that I'm useing....but I find a iris to be helpful in all instense's ..it sharpens your view and when used in conjuction with a blinder on the off eye it really helps you get target fixated...Somepeople say it helps and some dont ..I guess its a personal thing....punch a very tiny hole in a piece of black tape and stick it on your lense in line with your eye....the hole must be 1/16-1/8 in size and be a nice precise hole....leather punch works for this....then make up your own mind if you like a iris

Bob-Riegl · Post by **Bob-Riegl** » Tue Aug 14, 2012 3:29 pm

I use a Merit on my shooting glasses to make the dot on my Ultra-Dots sharper. Now I use the "power" setting of (1) for indoor ranges and this renders the dot tiny without any glare, but the iris helps to sharpen the dot even further. This works for me---simple, uncomplicated, no BS answer. "Doc"