The 49mm C2 Blue Color Correction Filter from Hoya cools the ambient light entering the lens by 200° Kelvin (-20 mired shift) by adding blue to the overall exposure. This filter helps fine-tune the color or look of a scene to match a film's white balance. It is helpful when using tungsten-balanced film and the light source is warmer than the traditional 3200K, or when a specific amount of color correction is needed to match a film type. Candles and low-watt incandescent bulbs are examples of warm light sources. It can also be used when shooting at sunrise or sunset with daylight-balanced film (5500K) and the overall scene is too warm. The filter will help cool the scene for a more natural look.
Multicoat (HMC) filters are recommended for enhancing the performance of multicoated lenses to minimize reflection, reduce flare and ghosting, and result in over 97% average light transmission.