AI can spot enemies too easy without any assistance of binoculars or zoom-optics, even at far distances, camouflage and foliage do not affect their ability to spot targets.
My suggestions are to make the AI less like robots and behave more like human beings.
Add a Field of Vision Cone for each AI. If you are in close proximity to them, they will spot you quickly. If you are further away from them, it will take them longer for them to determine you are a threat.
AI should use their own binoculars or zoom-optics if they suspect threat is present in their field of vision but at far ranges where the normal eye has a hard time figuring out if it is what they think it is.