Originally Posted by Broz
I don't think of them as a focus. I use them to adjust out the paralax. In fact in some cases when all the paralax is adjusted out at distances like 1000 yards you may be slightly out of focus. But this is where the tightest groups are shot. If I am looking at a scope for long range the side paralax is a must for me. I have seen it work with my own eyes.
I can't even imagine trying to shoot precision with a high powered scope at any distance beyond maybe 300 yds without a way to adjust out the parallax.
Parallax is really noticeable under 100 yds and out past 300 with any high powered (over maybe 12X) scope I've ever looked through, not to mention the image focus.