An adjustable objective does focus the target your shooting at but more importantly it eliminates parrallax. Parrallax is when you look through the scope and the cross hairs appear to move when you move your eye. This is much more evident in higher power scopes. Yes you need an adjustable objective in higher power scopes for accuracy. The VX-III is an excellent scope and I believe for hunting deer size game the 4.5-14 is the best scope you can buy. If you are willing to spend the extra $$ get the target version with the side focus. You won't ever say I wished I bought the lesser $$ with the adjusable objective. Side focus is a sweet set up.