Flat
Looking at a deer, you perceive depth: the thickness of its body and the more distant background behind the beast. A 3-D perspective is natural. Field curvature induced by a lens or lenses is not. A wide-angle or “fish-eye” lens in a camera crams more height and breadth into the frame than you’d see looking at the field’s center with your naked eye. But this peripheral information has a cost: distortion. The center appears thrust at you; all around it recedes as if the entire field were a globe.
Solution: Keep magnification at 2-1/2x, no matter how much field you gain by dialing lower. A 2-1/2x scope has a field of roughly 40 feet at 100 yards, enough to show you a generous patch of hillside. At 200 yards you’ll see most of a herd of elk. At 50-yard jump-shooting distance, you’ll pick up a running animal as quickly as with iron sights, assuming you’ve installed the scope intelligently.