It's all too easy to state assumption as fact on the internet. If something sounds right then it must be true - is a fallacy that politicians usually find themselves committing; however, the sporting community is not free from misinformation (heck, I've made some blunders at times and have had to correct myself). His claim revolves around "optimal performance" and according to the author that is the "middle" of the zoom range of a scope, but he doesn't clarify which scope and instead generalizes to make it sound like all scopes fall into this behavior. God forbid he ever uses a 3-18x scope at 3x or 18x, he might not ever be able to see what he's shooting - I'm being facetious of course but I would never recommend a scope based on the middle of the magnification range. Also, not all scopes are made alike, so brand X's 3-18 may perform differently from brand Y's 3-18 throughout the magnification range. While some scopes may exhibit their best performance around the middle, this is certainly not true for all scopes, same with camera lenses, buy a cheaper lens and you may see IQ fall off at the extremes, but buy an expensive lens and you'll see excellent performance throughout the zoom range. I didn't read the whole thread so I'm not certain what the context is with which this advice was given, maybe the original post was looking at $200 scopes and this idea might have some validity there; however, for those within this community who are paying $800 and higher for a decent scope I do not think you need to worry about poor performance at the extreme of the magnification range, might there be slight falloff in light, resolution, edge to edge, etc. yes, but will it be enough to cause a problem with you not being able to hit your target - doubtful, and if it does, then let the community know as it could be you setup the diopter wrong or maybe did something else that would cause this behavior or you have a faulty scope that needs to be RMA'd or you bought a scope that is known to have these issues and maybe it's time to look for something better.