Sight in your weapon, press and hold Freelook key, move mouse around.
Now unsight your weapon and use Freelook. Notice how Freelook only works when weapon is not sighted.
Select Binoculars and notice how the player uses to immediatly, and when zooming out, the player puts the binoculars away.
I prefer the option of the player just taking the binoculars out and holding them in his hands. When I want to zoom, I press the alternate mouse key to actually use them, and pressing them again would bring them back down. Finally, pressing binocular key will make the character put away the binoculars.