Nikon Canada’s Chris Ogonek covers the basics for understanding the numbers found on all binoculars:
Magnification
Size of the Objective Lens
Real Field of View
Understanding these values, and how they interact with each other will make it much easier to choose the perfect binocular.
Binoculars 101 | Part 2:
How to setup a binocular:
Does the size of the objective lens have an effect on the depth of field of the area in focus, like a lens aperture would? For example, does a 42mm objective lens have a shallower depth of field than a 21mm objective lens?