The field of view of binoculars can be described as either "real" or "apparent", and they refer to two different aspects of what you see when you look through the binoculars.

Real Field of View (FOV): This refers to the angle of the visible field seen through the binoculars and is usually expressed in degrees. It's essentially the width of the area that you can see at a glance, 1000 metres from where you stand. This is directly related to the optical design of the binoculars and can't be altered without changing the optics.

Apparent Field of View (AFOV): This is calculated from the real field of view and the magnification of the binoculars. It's a mathematical formula that gives an angle which represents the field of view as if you were looking through the binoculars with a magnification of 1x. It's usually larger than the real FOV because it takes into account the magnifying effect of the binoculars. This value gives a sense of the "immersion" or "panoramic view" that the observer will perceive. The formula to calculate AFOV is: AFOV = Real FOV x Magnification.