Originally Posted by
RobinC
A peep sight is a term used to describe the rear sight on a match rifle, also called a Diopter sight, or even iron sights in some older quarters, it has a rear aperture if fixed of around 1.1 mm, you can have an adjustable iris which will give a range generally from 0.8 to 1.8 (some times more). On a rifle the effect of the rear aperture is to alter your focus to draw it closer to the target, smaller will draw the focus out, you want your concentration on a rifle to be on the front sight element, and the target clear enough to judge the aim, but not in sharp focus otherwise your aim is drawn to the aiming mark from the foresight element and that is the kiss of death to a good shot!
It is impossible to focus on two focal lengths at once, on a rifle you have the rear sight at a few cm, the front sight, at 85 cm ish, and the target at 10 mt, so you compromise and the ideal is accepted as 2 mts focal length. If you need eye correction with a rifle it is to a fixed ratio, of plus +0.5 dioptre ( a dioptre is the measurement used in lens's) over you long vision prescription, which will take your focal length to 2mts, some rifle shooters with perfect 20/20 vision just use a +0.5 lens to get better 2 mt focal length.
The same applies with pistol, the rear sight at arm length, say 70 cm, the front sight at say 95 cm, and the target at 10 mt. so you need a compromise focal point again. Unlike rifle where you are fighting to place your shot on a 0.5 mm dot, with a pistol the ten is 11.5 mm, so you can accept a wider tolerance of movement and location than with a rifle, but your alignment of the sights front and back, and vertical line, as it is a shorter sight base is critical, so with pistol the critical aspect of the aim is the sight alignment, so the best compromise for pistol is not out at 2 mts, but on the sights themselves and ideally the front sight, so depending on your arm length a focal length of approximately 95 cm to 1 mt with the examples I used above.
Being able to see the target sharp is not worth diddly squat! With the sight picture sharp, remember you can not focus on two focal lengths, the target will be fuzzy , if its not then your focus is being drawn to the target, which will be at the detriment of the sight picture, and that is also the kiss of death to a good shot, and you will not understand as you thought it was! But what happened was that you focused on the target, and the sight alignment wandered, and you did not know because you had let your focal length drift out to the target!
An Iris on pistol glasses produces a peep hole effect on the rear, and it will make your focal length longer, like squinting at something in the distance, this draws your focus off of the pistol sight alignment, another kiss of death and a bad shot will be the result. Shooting like other sports has its fashions, and manufacturers are happy to make kit to sell, remember most kit in a fishing tackle shop is to catch fishermen not fish, shooting is the same!
Many (most?) good shooters will have tried an iris, most give them up, most have one gathering dust in a drawer, or sold on to beginner, few stick with it, although some use it as focal correction instead of a lens, but its a problem waiting to occur.
There is another issue with young shooters who will confuse us all with their claim to be able to get a sharp focus on two focal lengths, sights and target, Hmmm? Wrong, Oh no they cant! What they are doing is flicking back and forth so fast as the sphincter muscle in their eyes are young and supple, they believe they have both in focus, but as they tire during a shoot it slows, and the problem aims occur, usually to their total confusion! Worst still as they age, the muscle hardens, and they are then really stuffed, and it starts in the mid twenties, in latter life they have to learn to aim correctly with a fixed focal point on the foresight.
Any one who wants to improve their aiming I'd advise to shoot on reversed cards, forget the aiming mark, don't need it, concentrate on the rear and front sight alignment, and the placement of that picture on the card, with the correct lens in your glasses focused on the foresight you should be able to shoot at least as good as with the card facing you.
Have Fun
Robin
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