Tommy Mason introduced intensive benchrest competitions for those wishing to improve their skills to become International Schuetzen Benchrest Champions. 
Mel a new shooter demonstrates he has exceptional skills with a scope calling the wind, holding off and consistent bench techniques. 
So how does one improve their acuity and precision using iron sights.
Young shooters have young eyes that have the ability to adjust to the amount of light and change focus automaticaly between short and long distances (front sight and target).
As we age we loose the ability of our eyes to adjust and we must learn how to balance and adjust for light and refine the focus between the front sight and target.
New young shooters believe they are better able to sight a target that fills the aperture.
However your eye improves it's acuity and precision if it gets enough light.
So we select a front aperture sight where the target fills one third to half of the aperture's area.
With the target not blocking the eye it gets more light and improves your acuity and precision.
Larger apertures makes your eye concentrate more on the front sight and your eye concentrates on centering the target. 
Smaller apertures makes your eye concentrate more on the target and you loose the ability to center it as well.
So the size of the aperture means you are both balancing light and changing the focus of your eye.
Lones Wigger the only shooter in the Olympic Hall of Fame advised the target can be a blur and if you have a stronger image of the front sight you will concentrate more on centering the target instead of your eye focusing back and forth between the sight and the target.
So having a sharp target is not the desireable thing to do.
To have a sharper front sight target focus I use apertures with thicker walls.
To maximize light and the acuity of your eye we also have rear sight apertures to make the most light available  - but not too much which will cause glare and impede your ability to sight.
To have the correct balance of light for your eye you need to adjust your sights as sunlight intensity changes when intercepted by clouds or as the sun goes up or down.
Rule of thumb: Sunlight is up - you need to adjust your sights up - raise the point you are aiming at to continue to have the appropriate point of aim.
I use an adjustable aperture in my front sight so I do not have to flip to different size fixed apertures.
I also refine the degree of focus by using an adjustable diopter.

The shoot went well.  Today was the 20 shot any sight bench and offhand matches.   Sue miller won  the bench with a 492. 3 of us tied with 491s.  Wayne had 2 more centers than Joe and I so he got second.  Joe and had identical scores   248/243 with the same center count but I had a 24 that was farther away than Joes by about 2 thousandths so I got 4th.  Sue had a 25 that was 2 thousandths in.  So close to having 4 tied at 491.  Don’t ask about my offhand.  I forgot to take a picture of the scores.  Maybe somebody else did and will post the scores.   

Jack

After having the orange bulls totally fade out after a couple of seconds, I switched to the black ones for the ISSA regional. It helped quite a bit but I was unable to see one of my 30 cal holes and lost 10 points. The 32 cal holes were not a problem. If I close the rear aperture too much I get a lightning shaped artifact coming from 1 o’clock to the center. When I looked through Wayne’s German diopter rear sight that has some magnification, all it did was sharpen the artifact. 

Also, I don't see any 25 cal scores. Did they drop the 25 class?

That's a shame, regarding the German match!!!

How did your 25 Hornet do?

Your not kidding Jack. A 5 shot group in an inch @200 yds looked pretty good with whatever 25 cal you were shooting. The conditions caught us all there.

I liked it when Wayne would set up his surveyor tripods  at 100+ yds and run then up as high as he could.  When I won the 20 shot scope bench in 2017 I had a repeatable condition with his flags and my close flag that I would shoot unless Tommy’s tall 100 yrd flags were streaming at more than 45 degrees.  The  flags were hardly moving for my whole 20 shots this year but the second target had the impacts going high right so much that I even adjusted the scope instead of holding off like I normally do.  Wayne, Joe and I shot 491s and Sue shot a 492 with one shot 1/32” in the 25 ring.