I broke this off from the Trijicon he vs I dot pro sight thread so as not to take that off topic.

In that thread and others there is discussion on sight dimensions from multiple perspectives but much of it on front sight width differences and some on how much light between sides of front sight and insides of rear notch. In the discussions the factor of how sight radius factors into the equation and how wide a front looks on a target when used on a long sight radius gun vs a short sight radius gun.

My question is how to determine how front sight width and sight radius interact? and how to calculate how different widths on different sight radii (radius's) appear?

Examples: A .115 width front sight on a long slide such as a Glock 34 or 17L will appear narrower to a shooter than a .115 width sight on a short slide such as a Glock 26. If a person likes the width appearance of X (say a Glock 19 with .115 width front sight) and wants the same when shooting their longer slide Glock 17L how much wider should the 17L sight be to appear the same to the shooter?

Now arm length plays a role so it would need to be added to the calculations or a set standard arm length be used. If an average US males is 5'9" tall he would have an arm length of approx. 26" from chest to extended middle finger. Using a Glock 19 with 4" barrel and the 26" arm length chest to finger tip equals an eye to front sight distance of 24 3/4". I chose a Glock 19 as it is the middle ground between Glock 26 and 43 and full size Glock 17/22. It is also close to common 4.25" barrel lengths of S&W M&P and similar guns.

Next up would be a way to calculate front sight width appearance in the rear sight notch or how much light is on each sid of the front sight when it is aligned in the rear sight notch with different sight radii (radius's).

Examples: If using a .125 width front sight and a .150 width rear sight notch width on a 6" sight radius gun you would have the same amount of light between the front sight sides and rear sight notch as a gun with a .144 width front sight and .169 width rear sight notch on a gun with the same 6" sight radius(these are Trijicon HD sight widths in second example). Both sight set ups use .25 wider rear sight notch than the front sight width. Now if the same sight set up is used on a much longer sight radius gun such as a Glock 17L then the longer sight radius would make the front sight appear narrower and thus also appear to have more light between the front sight and rear sight notch.

Since the rear sight remains mostly the same distance from the eye with most guns regardless of barrel length this may be easier to calculate. A Glock 26 rear sight is basically the same distance from the eye as a Glock 17L rear sight with minor differences depending on grip shape and using an apples to apples comparison of the same rear sight (i.e. Heine, HDs and others mount the rear sight at the rear of the slide and Glock OEM and others the rear sight is further forward) We are still talking about minor differences. I measured stock 3 dot night sights on a Glock 19/23 that have a long front sight and rear sight mounted forward like a stock Glock sights at 5.96 and Trijicon HDs with shorter front sight length and rear sight pushed to the rear of the slide at 6.08 for a difference of .12" so pretty minor.

These calculations or formula(s) may be easy for someone more mathematically inclined but it is beyond my capabilities. Any help in figuring out how to determine these is much appreciated.

Here is a calculator for sight height and changing point of impact for anyone looking up sight calculations later.

https://dawsonprecision.com/sight-calculator/