The K2 yellow filter is primarily used for black & white photography. The filter darkens blue skies slightly, giving clouds a little more "pop." The K2 also helps reduce the effects of atmospheric haze. Often used for subjects at intermediate distances. HOYA Multi-Coat (HMC) filters are recommended for enhancing the performance of today’s multicoated lenses. These popular filters minimize reflection, reduce flare and ghosting, and result in over 97% average light transmission. Filter Properties at a Glance Filter Factor: 1 stop Glass Type: Hoya Optical Number of Multi-Coatings: 6 Layers / 3 per side Hardened Top Layer: No Anti-Static: No Frame Construction: Standard Profile / Aluminum Front Filter Threads: Yes