Depth of field - Binoculars
Depth of field refers to the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. In principle, only the image on which the binoculars are focused is really clear and sharp
However, since people are fortunately able to see slightly blurred images as sharp, phenomena like depth of field occurs. The consequence of this is that the depth of field is not easy to determine. One person may think that a particular image is sharp and crisp whereas another person may find this same image unacceptably poor in quality.
The larger a subject is depicted, the smaller the depth of field. In other words, you can view a subject from the same distance with a larger magnification factor or view a subject from a closer distance using the same magnification factor.
Perhaps this all sounds rather confusing but if you remember that the depth of field depends on how large the subject is depicted, then you will have grasped the essential meaning. So, if you come closer with a lower magnification factor so that your subject appears the same size in both cases, then you have the same depth of field. In photography, the adjustment of the diaphragm is of great importance to the eventual depth of field, whereas this is not of any practical significance in binoculars since this cannot be adjusted in them.