On most of standard size binoculars models, there will be a thumb lever or wheel placed conveniently within reach so you can adjust the magnification without changing your grip or taking the eyepieces away from your eyes.
Enjoy a smooth zoom on the Essentials 10-30x50mm Porro Prism Binoculars, giving the variable power you need for different scenarios. A lever near the right eyecup lets you control magnification, and a..