Binoculars are generally used to observe the battlefield, gather information and locate enemies. Marine sniper-spotter teams have spotters with binoculars to observe and locate targets for the sniper. The UNSC binoculars have a digital display, which shows the temperature, as well as the distance to the target.
MJOLNIR Mk VI featured in Halo 2 was the first armor to have magnification system in-game. The Mjolnir Armor's binocular system featured in Halo 3 has the same radius as the one in Halo 2. The only difference is that it is more detailed and that it shows distance to the target. The Sangheili Combat Harness also has a built-in magnification system. Otherwise similar to the MJOLNIR's binoculars, it has a slightly different visor shape.