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Consistent sight picture

Posted: Thu Jun 12, 2014 4:36 pm
by svensta
I seem to have some difficulty getting a consistent sight picture in that although having the foresight in sharp focus is not difficult the black blob in the middle is not always as "fuzzy" between shots even though the foresight seems to look consistently the same.

I have actually found that to keep chewing the 10 ring up the black(target) is best perforated when it's not "fuzzy" at all but rather just a grey circle but can't get that effect regularly.

Is there a trick to this like focus on the inside of the foresight ring rather than outside of it...?

Posted: Thu Jun 12, 2014 8:49 pm
by ShootingSight
Two thoughts:

Seeing black fuzzies inside your aperture is not fully understood, but the only solution is to use a larger aperture. It might be there are micro errors in your eye that when the retinal image is the assembly of all parts of your cornea, they are washed out. But when you look through a small aperture, only the part of your retina directly behind the aperture creates the image. If that is where a micro imperfection is, it can mess the image.

I also recommend using a shooting lens that is +0.50 diopters stronger than any distance correction you need, or just +0.50 if you don't use distance glasses. This will focus your eye in the hyperfocal 'sweet spot' without the eye muscle needing to exert any effort, and will give you a more stable sight picture.

I do sell safety glasses with +0.50 molded in, in case you don't wear glasses.

Posted: Fri Jun 13, 2014 2:11 am
by RobStubbs
Focus and sight clarity is a difficult thing. As SS points out, you may benefit from opening up the rearsight iris. It's also possible your eyes are tiring and you're staring too hard for too long. Equally you may need a different prescription than you currently use (or don't use). Simply put your eyes need to be in a relaxed state to work best focussing on the foresight so as not to tire quickly.

The solution is to try the differences mentioned and see if they work for you (oh and write down the results for your records). You may also care to try changing the foresight element size - that may equally help you.

Rob.

Posted: Fri Jun 13, 2014 2:41 am
by KennyB
ShootingSight wrote:Seeing black fuzzies inside your aperture is not fully understood, but the only solution is to use a larger aperture. It might be there are micro errors in your eye that when the retinal image is the assembly of all parts of your cornea, they are washed out. But when you look through a small aperture, only the part of your retina directly behind the aperture creates the image. If that is where a micro imperfection is, it can mess the image.
Hi Art, I have been playing around with rear aperture size for a while and my current thoughts are that:

with a lens set for your hyperfocal distance as you advise, the size of the rear aperture becomes less critical as you don't need the small pinhole to give you all your required depth of field.
If you're NOT using a "+0.5 diopter over prescription" lens then all the depth of field has to come from the iris and hence the 1.1mm rule of thumb.

By opening up the rear aperture you are using more of the lens in your eye - going from 1.1mm to 1.5mm almost doubles the area of lens that light is passing through. So any flaw in the lens in your eye (or scratch on your cornea) is much less critical with a larger aperture.

Now, yesterday I was shooting with someone using a +0.5 lens and a 1.5x Eagle Eye and he was using a 0.7mm aperture. He was complaining about his sight picture so I had a look and it was less than optimal even when you adjusted the iris...
My question is - does the +0.5 diopter requirement still hold if you are using an Eagle Eye?

Regards,
Ken.

Posted: Fri Jun 13, 2014 10:53 am
by svensta
Just to add..... My vision is pretty good and I have never worn glasses.

I used to use a 2.6 mm foresight(too small). I switched to 4mm(too big). Now I am on 3.7mm which seems to be working OK. One thing I do know is that usually my scores on lightly overcast days (no wind thank you) are usually 10-15% better. Overcast conditions with no big contrasts of light/shade between myself and the target seem to work well for me and getting consistent fuzziness seems easier.

Re: Consistent sight picture

Posted: Sun May 06, 2018 7:08 pm
by Modena
I am having this same problem with lack of consistency in the clearness of the bull, my age is 41. It seems for any one shot, the bull will be clear, and for the next shot it may be fuzzy, sometimes the fuzziness is bad enough that it even doesn't look perfectly round, and I'm left to somewhat guess where the edge of the bull is. I know part of this is due to eye strain, because after I rest for 2-3 mins (with deep breathing) after 10 shots and then get going again, the bull is typically clearer again, but there is still picture inconsistency between shots. I have a lens (thanks Art) which is +.50 higher than an eye test suggested. I'm not convinced however that the eye test was correct.....but that is a different story.

I am having other issues also with position which I am looking to address, and I theorise that a good portion of the lack of consistency in the sight picture is due to tiny variations in position between shots, of either elbows or cheek.

I am using 1.1mm, I will try opening it up as suggested, to say 1.5mm.

As an aside, I also tried going larger with front aperture. The USA shooting chart suggests about 4.4 for my sight radius, late last year I was using 4.6, then went to 4.8 early this year, and even tried 5.0. Yesterday I went back to 4.6 and I think the fuzziness was occurring more often during the match.

Re: Consistent sight picture

Posted: Sun May 06, 2018 7:18 pm
by Modena
The above description is for 50M prone. This sight picture problem does not happen in 10M air rifle, nor in 20M prone.

My guess is, for 20M it is because there is only 10 shots (plus sighters) before you're getting up to go down range and change the target, so the eyes have time to rest.

For 10M air I am guessing it may be a combination of the target being so much closer, and between shots my head/body moves around a lot more than in prone, hence the eyes are looking at different distances a lot more during an air rifle reload than during a prone reload. ????

Re: Consistent sight picture

Posted: Mon May 07, 2018 3:36 am
by Tim S
Modena,

You aren't the only one to notice a difference between an indoor sight picture and an outdoor sight picture. I find I notice misalignment far more readily outdoors, something I put down to brighter natural light. I also want a shorter eye relief outdoors.

A good position certainly does help; what works when you're progressing through a 95 average, may no be stable enough for a 99 average.