The first number you see represents the magnification. If a pair of binoculars is 10x25, then 10 is the magnification.
It's easy to assume that 10x25 means that 10 is multiplied by 25. In fact, the "x" refers to the magnification. For a 10x25 binoculars, the "x" is 10 times the magnification.
Magnification tells you how many times closer the object will appear.
The second number refers to the objective lens diameter in millimeters. In the 10x25 example, "25" is the size of the objective lens.
The objective lens is the lens that is pointed toward the subject. It gathers light to make the images brighter. The size of the objective lens determines the size of the binoculars.
The exit pupil is the size of the hole in which light will travel through the eyepiece and into the eye. The exit pupil is calculated by dividing the objective lens number by the magnification number. In general, the bigger the exit pupil, the brighter the image.
Article Written By Shiromi Nassreen
Shiromi Nassreen has been writing professionally since 2005. She specializes in travel and outdoor topics, and her articles have appeared in various print and online publications, including "DISfunkshion Magazine" and Matador Travel. Nassreen holds a Bachelor of Arts in theatre studies from Rose Bruford College of Speech & Drama.