The C12 color conversion filter allows you to match the white balance of 3200 Degree K tungsten balanced (warm) ambient light sources entering the lens to match Daylight balanced 5500 Degree K films. C12 filters cool the light source by 2200 Degree K (-120 mired shift) by adding a very dark blue to the overall exposure.The Hoya C12 filter is helpful when: You are using daylight-balanced film and the light source is very warm and you want to to record accurate colors on the film. Examples of warm light sources are low power traditional light bulbs, candles, and some halogen bulbs.Less ThanbRGreater Than You are shooting a daylight balanced film and you want to create a day-for-night look. The extra blue cast will help give daytime that dark blue night feel especially on overcast days.Less ThanbRGreater ThanHOYA Multi-Coat (HMC) filters are recommended for enhancing the performance of todays multicoated lenses. These popular filters minimize reflection, reduce flare and ghosting, and result in over 97% average light transmission.