The Parallax Effect appeared in iOS 7 some people may find it awesome some simply call it the infamous feature. At first, you may like it but later you will lose interest in this “3D window”. Also some users with eyes sickness might find it negative or decreasing visibility.
How To Turn On or Off Parallax Effect:
You wouldn’t find in the Settings simply as Parallax Effect, because it comes assembled with other features.
To turn the effect on or off just go to: Settings > General > Accessibility > Reduce Motion if the button from the right is green then it’s activated press it to deactivate and if it’s white then it’s deactivated press to activate.