Visual acuity - Binoculars
Visual acuity is of great importance in binoculars, as it is in photography. The resolution or resolving power must be good in order to be able to render enough details. The edge sharpness is also of great importance.
In cheaper binoculars (and camera objectives), the edges around the image will be slightly fuzzy and blurred compared to the centre of the image. This is more of a problem with a camera since once an image is captured, it cannot be changed afterwards. However, with binoculars, you can scan the image as it were. You can therefore make as much use as possible of the best part of the image, namely, the centre. Yet, you will probably be irritated and disheartened if the edges show poor image quality.
Just to put this into some perspective, you can of course camouflage a lack of edge sharpness by limiting your field of view . If you do this, you will not actually notice that the image quality at the edges is inferior. Yet, in practice, it is better to have a larger field of view after all because then, it is far easier to 'find' a subject. And as soon as it is in focus, you can use the better part of the image, namely, the centre part, to see as many details as you can.