Field of view
The field of view is the width that you can overlook with your binoculars at a distance of 1000 meters. This has everything to do with the viewer's viewing angle. The larger the viewing angle, the greater the field of view. You can calculate the field of view by multiplying the viewing angle by 17.5.
Viewing angle = field of view x 17.5
The binocular's field of view is determined by the eyepiece used. There are 2 types of eyepieces: ordinary eyepieces and special wide-angle eyepieces. You can determine the difference by looking at the type (W = wide) indications. You can also calculate it yourself. Multiply the magnification with the field of view (in degrees). Is the outcome higher or equal to 60? Then the viewer has a wide angle eyepiece.