C# | Magnification on Weapon Scopes Only?

I would like to add a magnification effect to the lenses of my weapon scopes, while the rest of the players screen will be left uneffected by the magnification. I would like if the prossess is easly repeatable and can be implamented on multiple weapons and scopes with variations of magnification. I know that it is posible but would like to know how to perform it in C# but, if there are any other simplified methods suggest them, as I am currently learning C#.

I would like the effect to look like this.

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Use Render to texture, attach a camera to the front of the scope with a different FOV , render it to a texture at the back of the scope. (Unity Pro feature)